I'm going by how much money I'd need to invest inorder to purchase said skin. For example, if I'm at 0RP, I wouldn't use 5, or 10 dollars to get enough RP in my account to afford corporate mundo, I'd need to invest 20 dollars inorder to have enough base RP.
a 975 champ I can't just invest enough money for 975 RP, I'd have to buy the 1350 for $10 inorder to have enough.
So if you're "just going to buy the skin" you're spending that much for it to begin with as you need to afford it in the first place.
I can't only put in 12.63 for corporate mundo, I can only put 10s or 20s to purchase rp, and which is going to be enough?
And while yes, investing 50 all at once makes the value cheaper, the problem is if you're only buying one of the skins you wanted with RP, you're spending more vs. individual value.