
That's a high stud fee - I'd not seen them raised to the same extent puppy prices have but ...... For me, you pay for the service. When I had dogs at public stud, my contract stated under 2 live puppies didn't constitute 'a litter' and I offered a free repeat (not asked for another £750!!). I took my contract wording from the breeder of the first stud dog I used, out in America.
You've probably done your £750 I'm afraid (cost of the service only) but in my opinion, you should expect to be able to go for a repeat mating - at NO extra cost.
I had a miss with my foundation bitch but I paid the up front cost - and later discovered that the dog, bought by that breeder from another in America, had missed to every bitch he'd mated with once arriving in Canada. Obviously I didn't bother going back. But the cost of the stud fee wasn't anywhere near as much as you have paid, so I could walk away. And did.