There are 14,000 bars of gold in the stash. (The German prisoner states as much.)
The total value of the gold is around 16 million dollars. (Crapgame, once he gets "the Paris price" and corrects for the decimal point he misplaced the first time he figured it.)
There are 125 boxes of gold bars "after splitting with Oddball and the Germans" (Crapgame again, in the truck as it's being loaded.)
Each box of bars is worth 8,400 USD (Crapgame, in the truck, talking to Bishop)
Kelly's men are taking 10,500,000 USD. (Bishop and Crapgame)
Kelly's men are splitting their share 12 ways — 875,000 each (Bishop and Crapgame)
The German tank commander got "an equal share" (Stated by Kelly, during the face-off.)
The assumptions (and what supports them):
The bars are nonstandard bars, weighing either 20 or 24 troy ounces (depending on whether there are 12 (for 20 oz bars) or 10 (for 24 oz bars) in each box), rather than the "Good Delivery" standard bar or "kilobar", weighing 1 kilogram.
The way the bars are handled. A single Good Delivery bar weighs between 320 and 450 troy ounces — between 24 and 29 pounds. No one noticed any oddness about the German's dispatch bag — like very heavy weight in it. Kelly, and everyone else who handles a single bar, handles it easily with one hand. The boxes are shown holding either 10 or 12 bars (there's never a completely unobstructed shot to establish which it is), and the soldiers handle them easily — in some cases, picking up two at a time, one in each hand. Seen in this clip, starting at about 1:20 A box of 10 or 12 Good Delivery bars would weigh between 240 and 350 pounds.
The total value of the gold as stated: just one of the smallest acceptable Good Delivery bars (320 troy ounces) would be worth over 11,000 USD; 14,000 of them would be worth 156 million USD, not 16 million. Not only would Crapgame have had to misplace the decimal point twice, and not have caught the mistake the second time, but a single bar would be worth more than the value he explicitly gives to each box of 10 or 12 bars.
The value as stated of each box: each box is worth $8,400. At $35.00 an ounce, that's 240 troy ounces (20 normal pounds — there are 12 troy ounces in an avoirdupois (standard) pound). A kilobar weighs 32(and a fraction) troy ounces. At $35.00 an ounce, one kilobar would be worth $1120.00. There is no way to get $8400.00 per box using whole kilobars. 7 would be worth only $7,840; 8 would be worth $8,960.00.
Good Delivery bars are stamped and hallmarked when they're made. None of the bars we see have any markings whatsoever on them. They're all smooth, flat, and highly polished.
Everyone present (except the German tank crew who we never saw) got an equal share. There are 18 shares.
Kelly and his men (12 total) are splitting $10,500,000 equally (Crapgame and Bishop, talking).
A Sherman's normal crew was 5. (Wikipedia)
A Tiger's normal crew was also 5 (Wikipedia)
Oddball and his crew, and "the Germans" (Meaning only the tank commander) presumably get the same amount (875,000 USD each). 875,000 multiplied by 6 equals 5,250,000, bringing the total to $15,750,000 in 18 shares. Multiplying it by 10, to give each of the German tank crew a share, brings the total to 19,250,000. Crapgame calls the total 16 million. He might round 15,750,000 up to 16 million. He would not round over 19 million down to 16.
Oddball and his crew and the German accounted for 62 (or 62.5) boxes for a total box count to start with of 187 (or 187.5).
We do see three members of the Tiger crew besides the commander. They're in the background seen grabbing some boxes just before the commander says they're leaving to Kelly. So that's at least four Germans including the tank commander, so those three extra guys should be factored in.
The Stumbling Blocks:
Nowhere near enough boxes. Taking the assumptions above, there were 187 or 188 boxes:
14,000 bars, packed in boxes of 10, requires 1400 boxes.
Packed in boxes of 12, it requires 1166 full boxes and one partial box.
Nowhere near enough bars in each box:
14,000 bars packed into 187 or 188 boxes requires 74 and a fraction bars to the box. Not 10 or 12.
The value of the gold doesn't match up with the number and weight of the bars at the same time.
You can have 14,000 bars that weigh 20 troy ounces, packed 12 to the box, but that only adds up to $9,800,000
You can have 14,000 bars that weigh 24 ounces, packed 10 to the box, but that only adds up to $11,760,000.
You can have 14,000 bars that are worth $16,000,000, but then each bar has to be worth $1142.00, and you can't have boxes that are worth $8,400 each without having a fraction of a bar in each box.
1) The whole mess can be explained by a prop guy making the bars (non-standard, Nazi spoils, off-the-record bars by the way) too big.
2) The writers just picked numbers that sounded good, and no one did the math at all.
The aftermath of the heist
So, what exactly would have happened after the film ended? Clearly, Kelly and his companions could not have returned to the Allied lines, as they would face court martial or even attack by friendly units, as they are driving a German truck (and in Oddball's case, a German tank). There are some implications that their intent is to desert to Switzerland, where they could bank the gold and ride out the war. How they would return to the United States without being arrested, though, is anybody's guess.
Considering that Colt thought Kelly and his men were actually pushing through on their own initiative rather than trying to steal a bank full of gold, it probably wouldn't have been hard into fooling him into pardoning their unauthorized attack.
Alternatively, their idea may have been to hide the gold somewhere in Switzerland and then return and finish fighting the war, with the survivors returning for the gold later. They were close enough to the Swiss border that it's possible they zipped over, then came back possibly later that night or the next day, and during that time they could've thought up a plausible cover story to explain their absence to Colt. Then again, if this is so, why leave the "Up Yours Baby" message for Maitland, which would seem to suggest no intention of returning, as surely Maitland would know who left it?
The Tiger Tank Crew
Okay, so the film doesn't call the Germans Nazis at all, but they don't hide the fact that the town and bank are guarded by the SS, the guys who basically became the inspiration for all evil empire shock troops everywhere. Did they manage to just find the one SS tank commander and crew who had given up on Germany, or are the stories about the loyalty of the SS overstating things?
The SS, like any group, was composed of individuals. They can't all have been rabid fanatics. And even if they were, this is a fictional movie, and the SS guys we see in the movie are equally fictional, therefore their opinion of Hitler etc. is subject to the whim of the writers. Judging by the Tiger commander's conversation with the SS lieutenant, it seems obvious he's got a fairly cynical and pragmatic world outlook (the dialogue is untranslated but the commander's overall tone and attitude are one of extreme indifference bordering on dry bemusement).