Back in the day they were incredably powerful for the price, they also overclocked like a champ and it was pretty easy to get your ti4200 up to 4600 speeds (the 4600 sold for more than twice the price).
These days they are getting a bit old for really good 3D perormance but if you can do without 8x anti aliasing etc then they are still a pretty solid peice of work. They are also one of the best cards for outputting to an arcade monitor if you can't justify the expense of an arcade VGA and can't find a trident blade 3D (I couldn't in both cases)
In answer to the original post, you might want to look at the prices these things sell for brand new as well as second hand, they are dirt cheap now even brand new