I believe I spent around $110 (numbers are a little fuzzy so not perfect) for two, three bin racks without a watering system (DIY build). I got most of my rats from our local reptile store and another reptile owner locally who has her own colony. So I paid feeder rat prices for about 10? individuals to start. So I would round mine to $150.
I now only spend about $30 a month for rat food and bedding. I was spending $50 a week for rats.
We have 15 snakes who take different size rats and I am running an average of 1.4 in the colony. I definitely have extra rats that I freeze and could definitely downsize my colony, but I am working on multiple genetic projects that I don't want to loose as well as breeding for pet standards.