I keep asking myself the same question, given my reptile collection is not nearly as large as yours i feel like in the long run i could save money breeding rodents myself. But there is a few factors that will probably cause you to break even with what you would pay for just buying frozen. One as mentioned above, time is money and these rats are going to make a mess and need maintenance. Secondly depending on where you live you may have to heat/insulate the room or shed your rats will be living in, as well as cooling in the summer months as well! So electricity needs to be factored in as well.
The way i look at it is when i get a larger collection and i am able to order 500 medium rats at lets say (MADE UP PRICE) 1.25$ apposed to paying 2.50-3.00$ i am saving money on the rats! You might say "Oh well the money you saved is going to shipping" that is true. HOWEVER if i want to save money i have to make commitments somewhere because if i breed them myself the labor and everything else included is going to be WAY over 50.00 dollars!
That is the way i am looking at it.
If anything i will have a 4 tub rat system with 1.3 colony. Freeze the rats that are not being eaten and keep live for trouble eating when i start breeding. But i am a long ways away from this!