I know 280 robux makes one ad credit, which is aproximately 3 dollars; but I can’t figure out how the exchange rate works. 0.01 USD is the minimum max bid, and 0.01 Ad Credit is also the minimum max bid. So if an ad runs at a max bid of 0.10 ad credit, and a competitor runs an ad at a max bid of 0.10 USD, which one is deemed more valuable?
1 Ad Credit = 1 USD.
Subsequently, 0.10 ad credits is equal to and just as valuable as 0.10 USD.
You mentioned in your post that 280 robux makes one credit, however you say that it is approximately 3 dollars. It isn’t - it’s approximately 1 dollar, assuming devex rates.
What you are MEANT to do is to directly deposit money into the ad manager, and not buy robux as a middleman. The robux option is mainly meant for ‘larger’ developers so they don’t have to cash out just to reinvest it in the game.