Due to the high, yet limited demand, Hoodia exctract is NOT CHEAP. One month worth of Pure Hoodia pills costs around $50 (50 U.S dollars). You should stay clear of products that are sold for much less. The cheap Hoodia pills usually contain very little real extract, if any at all.
Naturally the quoted figure applies to a one month supply of Hoodia pills. If you buy a larger quantity, the cost per month will go down.
Also, you should avoid any "Free Hooida" promotions. There is no real Hoodia in most of these products, and some of them are just outright scams.