How much would a moon rock cost if it was for sale?

People will sell you a piece of the moon for $22.49, but no part of the moon can be legally bought or sold at this point except some rocks.

Tag: moon 
Thursday, February 02 2012
Source: http://www.lunarembassy.com/shop/en/shops.lasso?-database=aa654s5677556pr&-layout=US$_pr9981_en&-response=searchresults_en.lasso&-NoResultsError=noproducts_en.lasso&-token.trackindex=1763531&-token.rn=25028206&-token.cs=US$&-token.rs29=33&-token.rscd=LE&-