Why is the pricing of the AI generators intended to screw us over??

I was using an image to video generator and I tried to see the difference in pricing from 30s, 25s, 20s, 15s, 10s, and experimenting with 1040p, 720p prices. I was usually off by 1 exact coin when I tried to add another 5 seconds and I think this pricing model is very unfair! Trying  to make us purchase a way more coins when we don’t need and just extorting  us. also having a minimum payment of $10 to add more credits instead of manually paying what is equivalent to 50 or 100 coins is also very silly model.