The big question is stallions who are overseas that are available only via frozen semen, who did not have their semen frozen in the United States. As Equine Stallion Services (formerly EMCO Stallion Services), I used to offer all of the stallions with a live foal guarantee, as I wouldn't import semen that didn't have good fertility rates and felt that it was reasonable to offer a live foal guarantee to compete with US-based stallions. Per the recommendations of several board-certificed theriogenologists, the purchaser had up to three doses provided for the stud fee (one dose per cycle), and additional doses (up to four more) for $250 per additional dose (a mare without fertility issues, bred to a stallion with good fertility by a good vet should conceive within three cycles -- if they don't you need to change one part of the equation - the mare, stallion, or vet!).
The biggest problem came with people who either did not have access to a repro specialist or who did not want to use a repro specialist. Many people wanted two doses per cycle instead of one dose per cycle (only possible if you charge a lot more for imported frozen semen), and then there was the people who would use their regular farm vet for the first one or two breedings, then complain that the stallion wasn't any good, finally use a repro vet, then get the mare in foal. It became a nightmare to manage, especially after one very well known board-certified reproduction specialist in Kentucky told me that it "wasn't worth her time" to check a mare every 6 hours to breed with one dose of semen, and that it would reflect in the cost she would pass on to the mare owner. I'm now hearing of vets charging an insane amount of money to breed a mare with frozen semen (up to $3000 for one cycle - when I told my husband this [a board-certified theriogenologist], he asked where they lived, as he'd like to know where he could make this kind of money for one cycle, as it's usually around $500-$600 here in Ocala!].
If you could guarantee that people would use good vets (as is the policy for many stallion owners in France, one of whom would not allow me to import semen to the US because I couldn't guarantee that a specialist would do all of the breedings), I would be happy to offer a LFG for my stallions. It's sad that there are so many vets who will do the work without wanting to do it right.
ditto what Oakmont said. I do have a limited LFG on Neapolitano XXIX-18, a rare black Lipizzaner in Europe. His post thaw is 67%. Two took first try with 1 dose yet one mare isn't in foal after 4 doses/2 cycles. I'd say it's the mare or vet or both. It seems they don't observe the 6 hour window and want to bracket it with 2 doses, costing the MO $ and using up limited supply. Very frustrating.