Only bought once personally, and I'm assuming that's primarily what you're asking about here, so I'll say it can be perfectly safe depending on the seller. Dean Cook and Rainbow Carnivorous Plants both have eBay stores in addition to their websites, but there are also some other solid vendors like CCCP and The Heli Drop who deal primarily through eBay. Outside of that I'd just check seller ratings carefully, see if I can dig up anything on the seller on here, reddit, or the FB groups, and personally I would use Paypal with a credit card for a couple more layers of purchase protection - though that may not be feasible for everyone. Never sold on eBay but if I end up with a greenhouse soon like I'm hoping then I may need to look into it.
MaxVft wrote:There are a few sellers on eBay but I’d advise not to bother. You can get plants much cheaper and often at a better selection on official websites.
Sort of agree, RCP is a good example of this. OTOH, you can get some amazing deals if you know where to look. The Heli Drop is absolutely incredible for helis and the closest in pricing to Wistuba I've ever seen in the US, and Cook's does huge weekly auctions where you have a pretty good chance of finding discounts.