I'm switching to hydro on my next grow. I just bought two GH waterfarms. I have to buy nutes anyways, now I just use the same nutes in my water. The medium is reusable, soil should not be. Soil is messy to work with, hydroton and water are not. Once you get your nutes dialed in with the proper PPM, hydro growing should be pretty simple. The rate of growth is astounding and in 90 days, you can have plants yielding a lb a piece. Hard to do indoors with soil. I think that answers the OP question right there. If you place a value on weed, the more you have from your yield, the greater your profits are. Therefore, hydro is much cheaper to grow, simply because of the returns it gives you.