They definitely are not half as much as the other. Perhaps the 2ml are 2.1ml, and the 1ml are .8 or .9 You have to look closely when you buy from StC or TPC b/c sometimes they are not selling a full ml. I bought a .8ml from them before. When I sell samples on EBAY, I always put .1ml MORE than what I advertize to prevent complaints...I mean how much extra is that really costing me...