I do think it would be nice if it suggested the Creator's current sell price, but that also means if someone buys it for, say, 40ms, and then the Creator lowers it to 30ms, or changes it to 300kp or whatever, that'd be what the person selling it would have to sell it for. Which seems kind of annoying.
And like Reanimagpie said, things that are discontinued naturally sell for more. Maybe a middle ground where it stores the ms price for a specific CA for a month, and if it hasn't been listed in more than one month, you can put it up for whatever you like? Or something like three months. I don't know. I get that people hate price gouging, but this is just the natural order of the world when something stops being made.
I also wanted to add that it reminds me of Amazon (and other similar online store fronts) allowing you to buy things from other sellers. "This is available at x price from another seller!" So maybe it could show up in the CA shop similarly. "Another user is selling their copy of the skin for x price." And it'd also allow it to show the original listing price and when it was last restocked, and the person could decide if they're willing to pay whatever the Reseller has set as the price. So if something is frequently restocked, people can see that, and decide not to pay a marked up price. Easy.
Some games, like Mabinogi (MMORPG) maintain the sales history of an item for the past year. This includes how many sold at what prices during that time. So you can see how much people have paid for it, but also what price it tends to sell at best. This can inform both your buying and selling decisions. It's really great. And it means that even if something isn't up, you have a general idea of the price range, as long as it's been listed (and has sold) sometime in the past twelve months. I doubt something like that would be implemented here, but it would be nice. and solve a lot of problems.