Well the cost on the pump is really going to depend on how far you need to push the ferts. In my case I needed to push the ferts about 4' so I used a more powerful pump that I had sitting around. I think though that it was around $30 at my LFS. It was a tetra tec AP200
http://www.mops.ca/cgi-bin/SoftCart.....asp?E+scstore The tetra tec deep water ones may work well too. I like it because it has two outputs (one for macros one for micros) and they are both independently controlled with knobs on each side. Compare that to closer to $100 for a traditional dosing pump and you see savings. Most people may even have pumps laying around in which case it may only cost you a few bucks for the timer and some air hose.