While I certainly agree that impulse buying should be avoided, I realize that an impulse sometimes takes over. If this is at a herp show, and you still have time left before the doors close, then you can change it to an educated buy on impulse. In such as case I strongly repeat my earlier recommendations about walking around to herp society tables and dealers and asking questions about the type you want to buy.
I have to disagree somewhat with Seamus on this one, when he says:
But secondly, I hate the idea of an uneducated consumer. The thought of someone willing to buy an animal right then and there when they need to ask questions like "How big does it get?" or "What does it eat?" and "How warm should it be?" makes me a bit irate. If you don't already know what the care for the animal is... the basic biological facts, I'm not talking hard stuff here but... Size?! Come on! Go buy another animal and get the one you liked but didn't know about after you have some knowledge!
If you are new to herps, I strongly recommend checking on acceptable herps first, BEFORE GOING TO BUY ONE. First time herp purchases, by the newbie, on an impulse, are the worst type of purchase. That said about newbies, let’s move onto more experienced herpers. An impulse buy by a more experienced herper, on the other hand, is not anywhere near so bad. I say this because the experienced herper may see something that has caught his/her eye and fired up the old impulse engines really hot. What does the experienced herper do? As in your case - I imagine that a responsible experienced herper would checkout care sheets if available, and ask a lot of questions. One of my main points, from my earlier post, is don't ask just the guy from whom you think you will be buying. Shop around, and ask the same questions at each table you stop at where these animals are also being sold. Thus you will maybe find out that someone is lying, or that happily everyone has the same story. If everyone has the same care facts, buy from anyone of them, in other words go with that first impulse and buy the snake of your dreams from Seller # 1. BUT if the seller, from whom you are contemplating a purchase, says something markedly different from all the others - you have to put on the brakes. That is when you need to pull your head out of the methane gas chamber (that is where the impulse engines get their energy since they are primarily little more than brain farts) and think logically. Now ask yourself: If all the others said it grows to 8 feet why would this guy say 5 feet? (Or whatever it was.) If the care sheets say 8 feet - why did the guy say 5 feet? Maybe he does not know, maybe he is lying, or maybe his own never grew larger than that and he is speaking from personal experience (not necessarily lying).
The thing is, you could have and should have educated yourself enough at least during the show before buying it, and that means from more than just the one dealer. As opposed to Seamus, I see nothing wrong with an experienced herper doing this. I understand that sometimes we all act on impulse. I just try to keep it from being the full fledged ‘Scotty we need full impulse power NOW’ kind of impulse because the next thing you know you are in Warp Drive or even worse you Star Burst and everything goes to hell. Sure it would be smarter as Seamus says to do your homework at home before getting to the show. However, if on impulse, then at least check it out as thoroughly as possible before buying - don't throw all your trust into the guy from whom you are buying. When you do that the impulse has won out and everything can wind up smelling like one of those engines exploded after being fueled by Lima Beans.
Now don't get me wrong. I am not trying to say you were wrong and the seller was right in this particular case. I think both of you were wrong but for different reasons. Your being wrong can, in my mind, be excused at least somewhat. You were not wronging anyone, and as you are pretty experienced with snakes I am guessing that your impulse buy will not jeopardize the snake's health as might an impulse purchase by a newbie. Your intentions were good. As for the other guy - he may have purposefully done a wrong - and then again maybe not. Of course, if this guy lied to you, there is, in my opinion, no excusing such a thing and he was dead wrong. Confront him next time you are at a show where he has a table – don’t get into a fight – but question him about why he told you what he told you. Also remember, sellers often lie or sugar coat what they say - there is a bit of used car salesperson in us all - I guess. No excuse for it, it is not a good thing, but it is done, and it is successful more often when it involves an uneducated or under-educated consumer. In light of that, the Romans (back in ancient times) said it all in two words: "Caveat Emptor".
In English that is: Buyer Beware.