There is a shitload of cosmetic DLC, background music and gestures.
But, I've clocked in about 300 hours and never got promted to buy anything. I had to look up the DLCs and was suprised myself. You never feel like there's something missing and there are no mechanics you could speed up or avoid by paying money.
Also no paywalled monsters, missions or anything.
The vouchers to change your appearance are scummy, no question, but you don't see your character anyways. (If you play with helmets on.)