I have actually thought about doing it when I found the right mare. With that said, it's really expensive. I have priced it at least $4,000 bottom price, with a donor mare program(best option). Those programs lease out the mare to receive the embryo for a few thousand dollars then return around six months after foaling. If you want to do it, then the mare should be stellar because you might have to do it a couple times if the embryo can't be recovered or doesn't stick to the recipient mare. As far as age, I have heard before the 20s is the best for donating and ages from 3-11 for the recipient mares. I had talked to a reproduction place and when they first came out with embryo transfer programs the job cost an easy $10-20,000 and breeding world and congress champions. It's a relatively easy job, but it's very tricky as well as both mares have to cycle close together and timing is everything.
Proud Partner Owner of Me Too Radical, Top 10 PQHA Quality Improvement Program Futurity. Sire of AQHA, NSBA, and NRHA champions. Sweet, gentle, excellent mover, excellent temperment, and so much more. Standing in Indiana.