Doing 80B predictions a day for 500,000 conversions would make this the lowest efficiency ad platform I’ve ever seen by several orders of magnitude.
The actual attribution shouldn't be on 80B though. It's pointless analysing requests you didn't buy. There might be some value in using that data in ML to feed into a pricing algorithm, but it would be marginal and I doubt cost/benefit would ever stack up. it would technically be in breach of pretty much every SSP contract I've seen (although everyone does it).
There are 150B+ auctions each day, of those we participate in at least 80B and in those 80B there are at least 5 separate predictions, to determine the type of auction (1st price v 2nd price for example), determine the price likely to win, determine the likelihood of the placement being viewable, determine the likelihood of the user to click, determine the likelihood of the user to convert given that they click, and then we run these last 2 for each candidate (campaign, creative) that is eligible for the current auction. We obviously don't analyse the stuff we didn't buy but 80B IS the number of top level ML-generated prices from our system.
The budgeting and targeting rules don't apply to the 80B number and they are slightly different systems.