Yeah once they reassure you the snakes all have their vaccines, it's obvious that it's a scam.
At which point you can happily string them along.
"Really? Are the snakes in Atlanta or in Boston?" Whichever they reply, "My COUSIN lives there! They will come pick up the python right away! What great luck." and continue on as long as you like.
My favorite scammer string along was when I was assuring them my pythons were very good at road work and could definitely rebuild asphalt, since they handled shovels with their tails. Naturally.