As far as being a seller... there's no reason a seller should feel obligated to be a parent and see if the purchase is smart for the buyer(as in, can they pay their bills, are they spending rent money). It's the buyer who is supposed to be responsible for their own life.

As far as someone posting on the net "I want this snake but I don't have the money to buy it and XXXXX" then I have no trouble saying "Dude... save your money and buy it when you have the funds."

If someone sells something they own, to use those funds to buy snakes, I don't have any issue at all. That's why we own things. We buy it to enjoy it. If we don't enjoy it as much, we can sell it and use the money to buy other things we enjoy. Some people might play the guitar for a few years and love it and have pricy instruments... and then lose interest. Should they keep the pricy guitar forever? Of course not. So they sell it. It's no different if they sell it when they lose interest.. or they sell it when they see a albino BP they really want.