Customary it is a price of one puppy, OR an alimony puppy. I personally don't count on championship and titles of any stud. Yes, it's a great benefit, however, if you want to return the money you put into your breeding program, you should think beyond that.
Explaining: I've seen a stud - everything great, and I was seriously considering him (and a couple of others), but he had a litter with another bitch (very similar to mine), and the puppies were just... cheap. Much cheaper than the stud fee. I decided to stay away from that stud. Well, yes, he's a champion and everything, but why then the pups are so cheap? It might have been the following:
1. The owners of the bitch don't know the average price for a puppy of that particular qualities (they advertised here though);
2. There might have been a lot of puppies in that litter;
3. There was something wrong with the pups.
However, before I breed I already know what price I will be selling the puppies for, because I know what I will be putting in those puppies (microchips, Innova puppy food, vaccinations, etc etc), so why would I want to sire this litter by someone whose puppies are dirt cheap? Don't want to sound rude or material, or anything like that, but I would like to get my expenses and time covered as well, and I don't have Wal-mart parking lot puppies.
As a result, I picked a Sire that has all the health clearances, looks great, wonderful match for a standard, and his puppies are selling like hot cakes for $3200+.
So, I think you should go a little deeper than just titles for your own sake.
Maybe I'm on the bandwagon here but thats a pretty silly reason not to use a stud. I mean if he compliments the female, it really wouldnt matter what the pups brought. I have recently purchased a UKC CH female who is completely tested from a good friend and have a choice of two studs to breed her to. Title wise, the stud I am choosing will probably make the pups technically worth less because he isn't AKC titled due to an old injury that kept him from being shown AKC but did well in specialty shows before it ended his career. The other stud is an AKC CH and yes, that would make them worth more than the non AKC titled dog in the eye's of the disciminating pet producers. But instead, I am thinking with a much different goal in mind than simply dollar signs, I am thinking where I want my breeding program to be a few generations down the road.
In my breed, the standard stud fee is usually around pet puppy price (around $600) and that is even for an AKC CH, OFA, CERF and vWD'd animal. An untitled untested dog would be much much less, probably lucky to get $100-200 for a stud fee. With Scotties, I would most certainly be very concerned about vWD.