I'm going to be frank, most artists charging more than $400 for a cover (including commercial rights) are scamming you. Pic-rel (Nboarart) charges way below industry rates. You gotta remember there's a lot of very skilled artists living in very low income countries where cheap commissions at good quality do make them a strong living. If you can pay a month's rent by drawing well, you're gonna learn to draw really fucking well.