There is a lot of confusion about how much meteorites cost or are worth. This article from astronomy.com gives a pretty good explaination of the costs. Like most things the cost is based on supply and demand.
The most common meteorites generally cost between $3-$6 per gram while exotic meteorites filled filled with space gems or carbon based diamonds that contain life’s building blocks may cost $30,000 per gram (these are super rare.) Meteorites that originated from Mars or the Moon are also very expensive. The most expensive meteor on ebay.com has a buy it now price of $3,500,000. Its over 2000 grams and comes in at $1500 per gram. It is billed as the ‘rarest’ meteor in the world. More than half of the 1900 metorites for sale on ebay right now are selling for less than $20. Most of them are under $5 and the more expensive ones are ones that have been made into jewlrey already. I found this pretty comprehensive chart of prices for meteorites that details prices for the different types of metiors.