Recreational doses range from 1-5 grams of dry mushrooms depending on the species and individual strength of the specimens. Dosages for wet mushrooms will be about 10 times higher (10-50 grams). Because different species vary in size, the number of mushrooms per gram will also vary.
$20-$40 per 1/8 ounce. $100 - $250 per ounce.
Psilocybin mushrooms are illegal in the United States because they contain psilocybin and psilocin which are specifically listed as illegal (Schedule I).
The primary effects of mushrooms come from several active alkaloids they contain; the most common are psilocybin, psilocin, and baeocystin. Psilocybin is a more stable compound than psilocin, but is broken down into psilocin after ingestion.
Psilocybin containing mushrooms grow wild across the United States and in many countries around the world. There are also several species which are easily cultivated with a fairly simple and inexpensive setup. Most recreationally used mushrooms are cultivated rather than picked wild.