If it's not going to be a common thing for you, I'd say just use the sleeve pallets. If the collar is in the way, you can build up a little with card stock/neoprene/etc. And yes, we've printed tons of them with plastisol through 230 mesh.
Pricing depends on what's involved:
-If you're pulling/trimming tags, you have to charge for that. I assume you probably will remove these, but it's not a given. We've done some where the original tag stays intact, & print goes underneath. Also some where the upper mfr branding label is removed, but care label stays intact, then we add printed branding beneath. (FYI: If an original tag is left in place & you have to print under it, & you've built up your pallet, rubber bands around the pallet work well to keep the tag out of the print area - just tuck the tag under the band.)
-If you aren't printing sizing info, then label print should just be an add'l location.
-If completely replacing the care & sizing labels with printed ones, then WE still charge like it's an add'l location, and add appropriate fees for setting up each new size. (These are typically burned in the same screen in a way that facilitates a quick change, either by sliding the screen or the pallet(s) & taping off the already-printed area.)