That's happened to me twice in the space of 2 days now!
Buyer 1 ,makes low offer on Vinted, I reject and then the very same buyer ends up buying the same item I've listed on eBay rather than buying the asking price on Vinted.
Potential buyer 2 makes low offer on Vinted for an already discounted BNWT item, I reject and then they message a couple of times before telling me they will just get it elsewhere for full price. I block and they turn up on eBay a couple of minutes later with the same offer. I haven't responded and don't intend to.
I suppose the same people looking for something specific for a bargain price would be looking at both eBay and Vinted, but will it cost them more to buy at the same asking price on Vinted? I think I've only bought one or two things from Vinted a while back, as I usually just sell there.