Are these bikes any good? I was looking at this one: https://www.hmbike.com/index.cfm?cat=recon05
But since I have no experience with choosing a good bike, I need some advice. I'm not trying to go down the Himalayas with it, but I want to be able to get a good workout.

Looks like an ok beginners bike.

Yeah. Just one thing: how much does it cost?

Depends on your definition of good.

They are low, low , low end bikes. Not Wal mart, but getting close.

It depends on you cash position I guess

I don't know, the forks aren't too great but the compenent listing are pretty decent the Blaze has a Manitou fork and full XT. That isn't too crappy.

As others have said, it's an ok entry-level beginner's bike but I wouldn't expect to have to pay more than $250 for one.

What's a good price to pay for such a bike? I'm guessing 300 is too much?

Way too much. For around $300 I would suggest looking at the Specialized HardRock Sport, Trek 4300/4100 and Giant Rincon. MSRP on them is a little higher than $300 but you can usually find them at a lower price on sale. Also, look at last year's models. For the around $250 price range, I'd look at the Trek 3700/3500/820 and Giant Boulder SE. There are of course many other bikes in these price ranges too. Check out bikes from K2 (can be found at REI) as well.