For rainbow dash you could probably get $3-5
Rainbow treat has been going for a bit more lately. ( I’m assuming it’s because of Christmas coming up?) In the past month or two on eBay, I have seen her go for $60USD+ international shipping rate MIB so my guess would be around $30-40 for a minty rainbow treat but you will have to check that with another member. You will probably get more selling to the US as those were never released there.