I'm glad to finally see a wide-band set up on the market. Sure the average guy could build one, but for the $350 it costs, it's hardly worth all the messing around and trips to the electronics store.
v8huntr is always finding the good stuff!
I agree that the price seems reasonable. $350 definitely seems like the going rate for a wideband meter. You could probably build a unit for about $200-$250, which includes $180 just for the wideband 02 sensor--that is, if you are pretty good at analog design. I really don't believe the average guy could build one though--the heater circuit and the sensor interface circuits are not trivial.
AEM also has a wideband 02 unit that goes for about the same price. I assume it's very similar (I don't know if it has data logging capabilities or not).
Dyno tuning your car lets you see more than just A/F ratios over the RPM range, so I would never consider this a replacement for good old fashioned dyno tuning.