I just purchased a TowerGarden used off of craigslist for 200 bucks including the cage, dolly, 1 gallon ea of nutrient, ph kit etc...

I've been a hydro hobbiest for decades and yes, I do believe the tower is worth 500 bucks.

Sure it would be better if it was 1/2 that but this is a small market. You just don't have the economies of scale at play here. It is well designed, proven to work, built incredibly well and it is built in the USA. This comes at a price.
While I'm no fan of juice plus who sells it, I do applaud them and future gardens for building it in the US and plan on purchasing another one soon.

As far as the DIY guys are concerned, I think they're all awsome and there is nothing like building it yourself. Anyone that promotes our hobby and gets more people into it makes a contribution to all of us.