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I'm not completely sure that it fits, but my first thought was Crack is Cheaper.
100% Loot Boxes for the random drop form; the gambling aspect is the core of the trope, not dropping repeats is just one of the less cruel ways to do it.
Crack is Cheaper applies when the Microtransactions hit the point of excess. The escalating price form is rare for real money because it's pretty blatant exploitation, and even with in-game examples there's usually a lampshading of how sketchy a business practice it is.
Crack is Cheaper is In-Universe Examples Only, so
Trouble Cube continues to be a general-purpose forum for those who desire such a thing.
Here's the setup. You have a event where there are a set number of items available for purchase, with one extremely valuable item as the end goal. The first item is free, but each item after that costs an increasing amount of either in-game currency or real money. Alternatively, the items have random chances of being picked up with each purchase, with some being harder to get than others and the end-goal item having the least chance to be pulled early; you pay your money/in-game currency and see what it gives you, paying more for each pull as you go.
This is a variant on Loot Boxes but I'm checking to see if it exists as its own subtrope.
Edited by Willbyr