There have been several posts under various topics about lights/stands/shelves used for starting seeds, so I thought I'd share my relatively inexpensive solution and hopefully prompt others to share for those looking for solutions. I found this link a few years ago and used the basic design for my shelving unit: http://www.tsflowers.com/plantstand.html
I did make a couple of changes. Instead of 1" PVC I used 3/4" SCH 40. There isn't a big difference in price, but the 3/4" seemed heavy enough for my use (and has been). I would note, all I use this for is starting seeds in 1020 flats, if you want to use this for lighting larger plants and pots, you would probably want to use the 1".
For the shelves, I got rid of the three horizontal cross members and added a third shelf rail in the middle. I did this so that I could place single flats parallel with the lights if I only had one or two flats. That way I didn't need to use both lights if I didn't need them (refer to my pics) and more importantly, I didn't need to buy/make any material for shelves. As in the original design, I can place 12 flats total on the shelves with 6 four foot florescent lights. The top shelf comes in handy for storing other materials. With this design, you don't have to build it as high as the original if you don't need that capacity and if you wanted to you could go higher if needed (probably would need to use 1" for more strength).
Measurements for my shelves are 51" long, 14" wide and 16" height between shelves (all measurements center to center). If you wanted to, you could increase height between shelves for growing larger plants. Lights are hung from eye hooks and are fully adjustable.
I didn't keep track of the costs for mine, but the original estimate of $100 - 120 is pretty close depending on how many lights you buy and whether or not you have a timer and powerbar you can use. Approx $10 each per light, about $30 for the PVC and fittings, a couple of bucks for eyehooks and the costs of timer and power bar.
Hopefully, from the original design and from my pics you can make your own if you so desire.