Im a veteran mushroom grower.
and i was selling dirt cheap at $7-$10 a gram. and i know people who were turning around and selling them for $15-$20 a gram. crazy in my opinion, i would never pay that, but people would buy them. i had a regular guy who would buy at $200 an oz. and he would turn around and make that oz disappear over night.
i heard once the rule of thumb was half price of whatever good weed was going for.
it dosnt cost too much to grow, if you do everything yourself. the most expensive part is getting a pressure cooker. which i recommend the 23-quart one on amazon for $81
http://www.amazon.com/Presto-23-Quart-Aluminum-Pressure-Cooker/dp/B0000BYCFU/ref=sr_1_1?ie=UTF8&qid=1313089454&sr=8-1
besides that u just need some canning jars, some wild bird seed, some "vermiculite" some free "tyvek" envelopes from the post office, and a coffee grinder.
and your ready to get started.
after that you need some plastic totes to grow in, no problems.