I have two coloniees of mice goign right now, 1:3 and 1:4. I feed them a wild birdseed (10 pound bag about $6, lasts about two to three months..), mixed with some nutri-bloc and dogfood without dyes or preservatives (about $10 for both together). The ratio is about 10 parts seed, 2 part nutri-block and 2 part dogfood. My colonies seem to be doing well with this food.
Right now I have a litter of 14 and 9 (third female has had babies, but haven't counted them yet), other box I don't know the numbers of babies, as it's a new colony and I didn't want to bother the new mothers by poking around counting babies a day after they had some. All seem to be very healthy with this mix so far.
The dog food is also used for my rats and I buy a 5 pound bag a month, though I am thinking of getting the larger bag and cut down the cost a bit.
Every 6 weeks or so I was getting about 30 weaned mice, after some are culled to feed my snake. With the two colonies going, I expect to get double if not before, since I have 4 more females then I did before.