i did mine for only 80 dollars (if i remb correctly). did it like almost 6yrs ago.
however i lost the contact for the foam.
Everything DIY. Buy abt 5 cm think foam, the person will recommend u the density of the foam according to what are your soundproofing needs. It is not those egg try ones, but just a flat piece of foam. Buy heavy duty Glue, and stick up on the walls, doors and windows. To beautify the place, before sticking them up, use a nice color cloth to wrap around the foam. Also i got a carpenter to do a platform for me. Below the platform is one carpet, on the platform is another carpet. It has served me well thus far, no complains, and the foam help cut alot of the highs of the cymbals, so the overall sound is very comfortable.