while I agree w you- I wouldn't do it- I'm curious what cost you know of. I could find no evidence the uterus reacts more than slightly, it's not a full engorged organ that would make for big blood loss. So please share!
Dear,last year when we rescued the pitt ChiChi,I realized she had false pregnancy and ended up immediately at the vet. First of all, the spaying does not put an end to the false pregnancy and also extends it. By removing ovaries during spaying,makes the prolactin collapse while the body still secrets progesterone. Therefore you will witness heavier symptoms such more stress for the dog and even more swollen breasts for longer times which can result another operation to remove them. Why take such a risk. I don't remember exactly but it was a stressful 3 weeks for us and later on she was spayed. They said that even after spaying it may repeat but she did not have it again.