Market determines the resale price, retail price is almost irrelevant in most cases. And like cyc said pretty sure the base models usually sell out at retail. People shopping second hand sneakers are looking probably since new ones are too much or they want a rarer model. It took me months to sell staple white GAT mids new but my used green ones sold in a day or two. And there is also the perception from a lot of people that items being sold not from a store much not be good in some way. I don't know how many times I'll get an offer at 25-50% of asking price saying that since the shoes you are selling aren't from a store they cannot be new and therefore are used so I'll give you a good price of xx.
I think if you just take 5-10 pictures with natural light both shoes should sell pretty quick
And regarding grailed I finally listed a good amount of stuff there and sold one item and got one lowball. Probably on par with SF I guess though site is much easier to browse