Yes, ATS-34 blades can be very good. The price of knives depends on a large number of factors (thickness, grinds, size, shape, handle materials, manufacturing costs, BS, etc.). The type of steel used can be a factor in the cost of the knife, but companies using ATS34 are paying about the same for a sheet of steel.
The working properties of any blade steel are determined by the processes of normalizing, annealing, hardening, and tempering. Most high carbon steels can be heat-treated in such a way that it will perform very well as a cutting implement, OR, very poorly. Some companies do a much better job than others with their choice of blade materials, design, grinds, and heat-treatments.
ATS34 is a very good blade steel. There are others that may be even better (eg. 420V, 440V, and low chromium steels like 52100, and 5160). There are a lot of different blade steels. ATS34 is one of the good ones. There is No Best steel. Of course, there are some poor blade steels (420J comes to mind).
I would suggest looking very hard at the knives from Spyderco. I'm sure you would be very pleased with something like the Spyderco Wegner folder in ATS34.
Paracelsus, confusing the issue
For more steel and knife information, look at the articles linked
here.