Yup...happens all the time here. I've seen so many Mom's buying ...for $5 a tiny tank with 2 hatchling RES in China Town near the ferry. Then they'll go home and think they are up-grading and buy a ten gal tank. When they see how many times they have to clean the tank and change the water, and how big they're getting....also how bad the water smells when you don't change it...out they go. Most people here dump them in the big pond near me. A horror for sure!
Oh yes Nay. Usually on the Manhattan side of the ferry and even sometimes on my side. There are so many food markets there with different kinds of turtles in some kind of nets that they sell too. Whenever my son goes there in the Summer he buys one and ......not going to say what he does...a no no...but they get a new home. I don't say anything to him about this...not my business.
I have wanted to do what your son does (except I would be hopefully nursing them back to health and keeping them).
Nay, have you ever thought about when one of those types of ads appear, doing an "ad" telling how to properly care for turtles? Might reach one or two folks with information that way. Just a thought.