Hamwild I am not always looking for rare things. Just cool things. Some plants I cannot send out of state 'legally'... if they have ever been in soil or even sat in their containers on the ground here in lovely pest filled Florida they are considered to have been exposed to nematodes and Imported Red Fire Ant and almost without exception (especially in the Southern Tier) would technically be illegal to ship over state lines even if no money changed hands. If they decided to stop the package for quarantine it wouldn't have a happy ending for me or the plant.
Other things that are grown soil-less (like epiphytes) and cuttings are probably ok. But things happen....once I sent a bromeliad trade to my friend (this has been years ago) who lives in Ohio and there was a hitch hiker little green tree frog down in the leaves hiding that I totally missed when I packed it. We laughed about it but I guess I was actually guilty of exporting an exotic to another state LOL.
We used to always label the boxes with 'Live Plants Please Do Not Delay' or 'Please Protect from Extreme Heat or Cold' and also 'Can be opened for inspection' to show we weren't trying to slide stuff by the USDA and once they actually did stop something I sent to a friend and held it in quarantine for a week.