Honestly if you are thinking about it like that, then you should probably get out of breeding. A lot of people do it because they enjoy snakes and the excitement of 'Christmas Day' when you get to see the babies and what patterns/colors you got. The selling end of it just covers the cost of the enjoyment and excitement. I mean sure, some people make a living on it but I imagine for most, it is what I already stated. At least it would be like that for me if I bred boas.
And I don't breed but I will say the single biggest expense even for not breeding is feeders. My snakes are garbage cans especially my retic who is just bottomless. I have no idea where he hides so much food in such a skinny little snake lol.