Okay...the Bondsmagi are this all-powerful society of magicians, whose services are horrifically expensive. That said, when Capa Barsavi started having trouble with the Gray King, why didn't he even think of hiring a Bondsmage or two of his very own? I'm sure he could have come up with the money.
Normal people—even the Right People of Camorr—just don't think about Bondsmagi. It's not the kind of thing that would occur to anybody—it took Locke knowing there was a Bondsmage and lying about it to make Barsavi even consider the possibility. The only reason the Gray King hired one was that he was a junior Omnicidal Maniac...he didn't care what happened after he got his revenge.
Also, the cost would have been to prohibitive, even for Barsavi. Remember, the Gray King had been saving his money and planning his revenge for decades, and he still needed to steal the Gentlemen Bastards' wealth, that they'd been hoarding for years, to hire the bondsmage just a couple extra days to finish the job.
That makes no economic sense. The Bondsmagi hire themselves out; that means that they must set their prices low enough that *someone* in the world can afford them, otherwise they have no customers. Sure, hiring one for a day can cost more than a lowlife labourer will earn in his life, but it can't cost so much that the likes of Barsavi can't afford it. Think of private jets: They can cost so much that an average middle-class slob can't afford one, but they can't cost so much that Bill Gates can't afford one. If they do, the company making them goes out of business.
It's heavily implied, by Chains in particular, that the Bondsmagi don't actually rely on being hired by outsiders as a meaningful revenue stream. Their prices reflect their vanity; they'd rather have it be widely known that their services cost an unfathomable sum of money than actually be hired by someone willing to pay that sum.
Not really. It is, at times, implied the Bondsmage basically have their own nation/organization. So the non-bondsmagi handle day to day stuff, whereas the Bondsmages are hired by kings and what not. Also, there is nothing saying there isn't an exponential curve. Relatively cheap for a spell or two, super expensive to have on retainer for a month.
And Barsavi had hired a Bondsmage before...remember when Locke drank Barsavi's toast, with the enchanted shark tooth in the glass?
The Bondsmagi seem to work like a guild, I doubt they would accept jobs that put them against one of their own. Barsavi could have tried to hire them and they refused on a pretext or intentionally set a price that Barsavi can't pay so they don't get involved on both sides.
For that matter, why didn't someone who was mad at the Sinspire hire a Bondsmage to clean out its vaults? These guys are apparently for hire to people with the right money, and I'd say that offering one 90% of all the money in the Sinspire to clean those vaults out would more than purchase his services.
But not your life. Requin would find you, and he would kill you, and then he'd go to work on you. Sooner or later the money would run out, the Bondsmage would leave, and you'd be screwed beyond the screwing. Disproportionate Retribution (and it wouldn't even really be disproportionate!) is a fact of life.note Unless you can kill Requin first, something which he expects and is prepared to defend against Plus, see above, about Bondsmagi not being part of the average Therin's experience. And, "if you do all the work you can have 90% of the money" isn't really an offer, it's a joke.
Most of the "Bonds-magic" is an art of deceit, treachery, hypnosis, telepathic manipulation and illusion, it's said in the first book this way they had slain the Therin Empire army. There is no hint they could break Elderglass, the substance which no human art may mold.
I did wonder for a while why the Bondsmagi, if they're so powerful, don't rule the whole world. Then again, they could be going by the RL and Angelique principle: "World domination? Who wants that headache? Let's make gobs of money instead!"
Word Of God has given a couple of answers and assurances that we'll find out, perhaps even in The Republic of Thieves. As to the answers: "How do you know they don't?" "Maybe there's something they're not telling us?" and "Maybe they just can't agree on how..."
They might be like the faculty of a university...and getting the faculties I have had to deal with to agree on anything made herding cats look ridiculously easy.
If you remember the canon version of how they were founded, this makes sense: A strong mage went to a weak one and said "Join me or fight me," then the two of them went to a third and said "Join us or fight both of us" and so on. It's not like they have some overwhelming philosophy that binds them all together, it's a combination of fear of what would happen if thye left and liking being more powerful than everyone else.
The interlude on them told how Therin Emperor had tried to subdue them by other means than force. They answered with a letter which said they were ready to work for everyone given the appropriate (for any other Therin, egregious) amount of money, or to kill at the slightest provocation.
The easy answer is that they're not actually all-powerful, and let their reputation do most of their heavy lifting: they're Shrouded in Myth. Granted the Falconer was very powerful but Locke and Jean did get the better of him in the end and he was implied to be very high-ranking within their organization. Combine that with a healthy dose of infighting and possibly no particular desire to rule the world to begin with, and it makes sense.
Speaking of the Sinspire—-I wonder if all that cash is really there, or if Requin, being the smart cookie he is, has most of it (except for enough to cover the Sinspire's cash outlays) invested somewhere? He'd probably think it was a wonderfully funny joke for someone to go to all the trouble to break on in there, only to find that there wasn't nearly as much money as rumor had claimed.
It would certainly make sense, and fit Requin's character. The Sinspire is as much a bank as it is a casino, if I recall correctly, and Requin doesn't seem like the type to hesitate on making money by giving out loans.
Based upon the magnitude of the Sinspire (as a bank and a casino), it is unlikely they have ALL the money there. But even if it is just a small percentage (enough to handle someone withdrawing the entirety of their largest single account, for example), it would probably be a massive amount greater than any thief had stolen before.
And based on the descriptions of the vault, it makes perfect sense to keep all the money there. The vault is unbreakable. Locke and Jean are quite possibly the two most skilled burglars in the world and they consider even looking at that vault to be suicidal. And again, it needs to be said again, Requin makes a decent side income renting space in that vault to people who don't feel regular banks are safe enough.