people always ask for a lot when you want to dex the newest totum
That's really not fair, I almost always see free or cheap dex threads after MCW. For the breedable ones, if you wait a couple days the price drops pretty significantly or you can even find them free in the shelter/wonder trade. If you really feel this is a problem you need to be accurate or there's no way to judge the true nature of the problem or how to best fix it.
Since all the MCW releases eventually have alternate ways to obtain them (totem scouring, variant special breeding method, mega stone voucher) I think it's pretty fair. If you really need the dexes for Arceus then you're probably active enough to get it yourself or trade for it after. If you're not, then surely the wait is a little easier to bear?
(Also yes I know the vouchers aren't cheap but that's the case for the cannon stones too, I'm pretty sure you're intended to trade for some of them)