Re: Concept 2 Model B
$200 is little high for a model B unless it's in great shape and hasn't been used much. Model B's stopped being made in 93, so it's probably close to 20 years old.
I had the same question a few weeks back and based on previous discussions on this board, it seemed like $100 ballpark or less for a Model B was worthwhile. I found a Model B for $80 a few weeks back on Craigslist, then basically re-built it with new parts from Concept2 for another $120, making it a $200 purchase for me as well. It rows very nicely and is essentially a new rower since the flywheel and monorail are in good shape. It came with a PM1 monitor that works fine. I am very happy I bought it.
Getting a new PM3 is $160 from Concept2 so keep that in mind since it's difficult to track progress without a monitor. Then, if you upgrade/rebuild it like I did as well, that would be pricey for a Model B and you're probably better off finding a used C or D if patience/luck works out for you.