Spay/neutering can be done for much less than $400. Check with your local shelters. I think I paid $28 for my cat. The rest were adopted from a shelter already fixed for ~$50 each.
It would be better for those cats to all go to a shelter than it would be to adopt them out unaltered. They'll be fixed, vaccinated, have their health checked, and the new parents will be vetted for suitability. People who can't afford to pay the adoption fee for an altered cat at a shelter absolutely cannot be trusted to alter, or even take good care, of a cat on their own. It just won't happen.
Sending those cats out with the ability to reproduce is guaranteeing unwanted litter after litter after litter. It would be more merciful to put them all down now than to have to put down scores, maybe hundreds, later.