Yes shipping cost like $45 and you have to buy like 6 months worth but...
say you buy 100 weaned rats (30-44 grams) with shipping it will cost $135.74
to buy those same 100 weaned rats at petco will cost $367
I don't see how saving $231.26 isn't worth it.
as I said before the money you save will buy you a second freezer just for them, cover the cost of shipping, and still leave you with more cash in your bank account at the end of the day.