To be fair, there are also bundles you can buy, both for plat, which makes each unit of platinum less expensive, and for skins, which makes each individual skin cost less platinum - further reducing $ cost for each skin.
The Ops are the only thing that should be priced fairly, because it’s new content and also new sources of gear … but even then the season pass saves you some $ and gets you hero keys saving you credits as well.
But skins are purely cosmetic. The price point on them is typically set based purely on maximizing $ earned. If they were $0.50 each they’d sell them to a lot more people, but make much less money overall because of the low price point. And the more money they earn from skins, the more they can spend on updates, bug fixes, and extra free content like new modes.
If they’re not your cup of tea, then you don’t need to buy them … but please, rather than dissing the devs over the price point, thank the people who DO buy the skins, because they are in fact paying for YOU to continue getting free updates without spending another dime on the game.