I have heard alot of people say they want more subs added in an add-on. Fair enough.
Lets say 6 months after release they add 3 subs in an expansion, and the box costs $30. I bet there would be a general "WOOHOO"

among those actually playing SHV (those who didn't buy it don't count, sorry

).
Now lets say you are the kind of guy who really only likes Type IIs.. we have a few people like that and I tend to be one of them (but I like VIIBs as well). Now you may say to yourself.. 3 subs.. $30. I only want one of them, why can't I pay just $10 for that one?
BTW, if you bought SHIV Uboats add on, divide that cost by the number of subs included and 1 patch (which was ONLY available through a purchase). You will then have a unit price for each of the items you bought in a bundled mico-transaction.
We have already been doing it for every game we have ever bought an add-on or expansion for, just under a different name.