they are pretty good. good power handling, work well in small boxes. easy to implement because they have a large response range. they can get pretty rowdy too!
they do have a bit of a hump in the 50-60hz range so they are a little more oriented for street bass. they are a solid all around sub, but they are pretty much interchangeable with most mid level subs. (think of jl w3 type subs)
i have seen them go as low as $30 each, but realistically 50-60 each is a reasonable price.
my ex-girlfriend said "its car audio or me"
i've had tougher choices at a soda machine...