Haggling is acceptable if you are buying a high priced snake and/or multiples and you are paying CASH. If you are buying snakes in the $50-100 range: don't try to haggle.
Haggling Tip: Count your cash out on the vendors display table and spread it out when you make your offer--Usually a crowd will 'shoulder in' to see what you are buying and the vendor will experience a great deal of pressure to successfully complete a sale. More than once I've had breeders turn my offer down only to be 'overridden' by their wives seconds/minutes later as they stare longingly at the money...