I've been thinking this over the past month or so, but do y'all think people would buy shell swapped joy cons and pro controllers for a premium, say $20-$40 more? I kinda had fun shell swapping my joy cons and think that if I get a bunch of parts and buy broken ones I could sell them for that price or even match Nintendo's pricing... That is if others would be interested in buying them. What do y'all think?
Maybe. What you'd be doing is selling refurbished controllers. I don't think anybody is going to want to pay the same or more for a refurbished controller if they could buy a brand new one. Doesn't matter that the shell is brand new, it's not an original part and may not be the same quality, battery may be worn, shoulder buttons (which are not included with replacement shells) might be visibly worn, used sticks, even if working fine, will not last as long as brand new sticks, and for that matter, 3rd party stick replacements probably won't last as long as original sticks either (unless you buy hall effect sticks but that will eat into your profit margins)
You may be able to make a small profit if you buy new controllers and swap to GuliKit hall effect sticks and optionally do a shell swap. You can sell the controllers as new (other) since all the parts are new and price it at a premium with the promise of no stick drift.
And you will be able to recoup some cost by reselling the brand new original sticks and shells you end up with as a result of the swaps. Nobody is really selling original parts and many would buy them over some no name Chinese brand.
Buying broken or worn JoyCons makes it a refurbish and people are going to want to pay less and you won't be able to charge a premium.
If you want to fix up broken/used JoyCons and sell as refurbished, then you will have to get them cheap in order to sell at a reasonable price and still keep your profit margins good. Buying promising bulk lots and watching eBay for listings going below the average price, that sort of thing. The price can vary a lot.