Actually he got a good deal. Those screens are more expensive because they don't come bundled with ad riddled toiletware, and they often have a longer lifespan to accomodate being on for so long every day. Depends on how much it got used already though.
Yep. You do need at least a sound bar, or a stereo system with these. But most inbuilt TV audio is pretty terrible to begin with, at least on low to mid end tvs.
Those were exactly my thoughts, if you are the kind of person who is looking for a commercial display for your TV, I doubt you would use the integrated speakers.
Even the cheapest, most bottom-of-the-barrel LCD monitors from 15 years ago seem to still be 60. Matching the refresh rate to AC cycles per second makes sense.