the previous time i kept reptiles i had about 40 pythons and a few other snakes and about 20 lizards. feeding purchased food would have been so expensive. so i bred my own. i had the space to do it. so i would like to point out the other side of the argument, the pros. feeding them is cheap, i used to buy bags of pig feed for £6 ($10) for 25 kilo (55lb) and supplement it with leftovers. occasionally a bag of carrots or apples, horse feed quality, helps the rat diet no end. if your breeding colony is big enough you will always have the right size. I made about £100 ($155) a month selling my excess rodents to the pet shops. this more than covered the cost of the rat feed. Another method is having a 'dustbin' pet. For me it was my group of tegus. No rat is too big for an adult tegu, but if you have a boa, a brum etc they will eat your large ones.

hope that balances things