Expect to pay about $500.00 for a light, hydroponic marijuana setup and everything else you will need to raise your crop hydroponically. You can spend more or less than that, but $500.00 is the average initial setup price for a personal garden (5 to 10 plants). Once you get things set up you can continue to raise new crops with your set up and only have to spend money on nutrients, bulbs, and other maintenance.
After a few crops (you will make mistakes at the beginning), your product will be better (if the seeds you used were good) than anything that you would normally buy, at a fraction of the cost.
If you do things properly, you will get about 1 to 2 ounces of premium tops per plant every 3 to 4 months. You won't have to deal with people that you might not trust, and your stash will be clean and healthy as can be.