Not very many relative to the other bowls, but how much did they pay for the rights to air it is the real question. If they didn't pay an exorbitant amount relative to what they sold the advertising spots for, then it was a good deal for them, no matter how many people actually watched it.
I've never actually seen any ratings info on these early bowl games, and I agree that not many people are watching, but I bet it is more than you think. It isn't like there's anything else on during these games (except last Saturday when there were NFL games on at the same time). A lot of people are hanging around their house this time of year, have family members from out of town in, etc., and if they care anything about football might have the bowl game turned on as background noise, checking in on it once every so often.
I do know this - if nobody was watching them, the roster of bowl games wouldn't have grown to 40+ over the years and they wouldn't have persisted like they have. They don't exist because they lose money.