That depends upon how much it was used in those 7 years since it was manufactured. If it was kept on 24/7, it may only have a bit of life left in it and only be worth the $150.
My family bought a 19" SDtv from a Salvation Army for about $20 about 2 years ago and I've been using it downstairs in my families house to watch tv. But now I moved it upstairs and have been using it more regularly and it's been a great investment.
When we first got it, it would make loud noises when I turned it on(sounded like something was hitting the glass screen from behind as it warmed up and would do it sporadically while playing), but it's been great for a while now.
We definitely got our $20 of use out of it, that's for sure.