While absolutely too many things are charged for in gaming today (exp boosts? skip potions? cheat armor that was already fully developed at launch? all ways to get your company on my high seas list).... in the specific case where (1) new content is continuously being developed AND (2) the game is not asking for mandatory spending to continue playing (e.g. no expansion pack to purchase, no subscription fees), I don't think the concept of charging for in-game content at all is abusive.
If I buy once and then a year later some optional paid cosmetics or other goodies are added, I think that's permissible. And if I'm in a free to play live service game, I recognize the ongoing dev costs need to get covered somewhere.
I do vastly prefer those companies that give their games TLC and updates for free, and I'm not saying the standard pricing for optional purchases in the modern market are reasonable. But I think the existence of in-game purchases, if not their current state, can make sense sometimes.