In this industry its only natural for the seller to sell their snake to the first person to send money over.
If they got paid every time someone inquired, haggled their prices, asked for PayPal info, then they would not need to sell snakes at all. You could have easily been 1 of 10 people inquiring about the same snake.
It's only normal to want to negotiate prices, but if the animal is of outstanding quality, low priced, or both, then it's important to try to pay as quickly as possible, if you have any questions try to calling them first so you can get all your questions answered in a minute or two, if they cant be reached by phone then refresh your messages every few minutes. You're likely competing with many others interested in the same snake.
In most cases though, sellers are willing to go down on prices within reason. Sometimes they'll go down a lot more than you think.