According to my numbers it is exactly .50 cents cheaper per box of 50 to load .40 S&W over 10mm. This is with numbers I use for my own reloads and should not be taken as an "across the board" index.They don't use the same brass.
Regarding the debate, I am not a fan of either gun originally listed in 10mm. The closest I have come is the AMT Javelina. I will try to post some pics here to show barrel support.