I sell mine at:
Pinks: $1.00
Fuzzies" $1.50
Pups: $1.75
Weaned: $2.00
Small: $2.50
Medium: $3.00
I sell aroud 150 rats a month and never have a problem getting rid of them. Just make sure not to sell too many so you have a good supply for your own snake collection.
Selling the extra rats completely covers the cost for food, bedding, electricity and I still make a small profit in the end. Its also a great way to make some good connections with local herpers.