The PRS-T3 is being sold on Amazon for $149 by a 3rd-party retailer, and according to the listing it first showed up about a week after Sony announced they were pulling out of the North American ebook market.
The PRS-T3, which launched in Europe and Canada last Fall, has never officially been released in the US. In fact, Sony stated that they weren't planning to launch this ereader in the US; instead they planned to focus on selling ebooks on tablets and smartphones.
So should you get this ereader? I would say no.
While the PRS-T3 will continue to function after Sony turns off their ebook store, there is little to recommend this device over other models on the market. It's rather expensive when compared to its competition (Kindle Paperwhite and the Kobo Aura), and aside from some software features there is little to recommend it.
In fact, I can offer at least one point against. The PRS-T3 is using a Pearl E-ink screen, and it has a touchscreen but no frontlight. That makes it a rare beast among ebook readers, and while I don't care to use a frontlight I would want one just in case.
There are better options on the market, I think.