If you grow organically\with the soil food web you should have no problems recycling your soil. It isn't being 'cheap' either, some amendments release nutrients for months or even a YEAR or more... much longer than your grow cycle. If you're just throwing your soil away after each grow you're just wasting money, and the environment.
You just need to separate as much of the root mass and extraneous matter as possible, you can set it out to dry along with the fan leaves from the grow and once they have dried out you cut\crumble them up really well and add them to the soil. Next add in some new amendments (these are various from meals to guanos, earthworm castings, compost, etc.) or dry organic plant food. It would also be good to spray it down with compost tea at least once or every couple weeks. Keep it moist but not too wet and leave it to cook for several weeks to a couple months.