I must admit to a black hole of understanding as I wrap my mind around titers. One day I will try to beat that knowledge into my head! I think it is because I need to understand the *why* of it and I don't.
Now about the cost of titers: Rabies a non export rabies titer is $276 might be more now and this is in Toronto Canada. An export titer is $500 and the last time I checked it out I believe England only recognizes Univ of Guelph. Note you will need to check out the rules and regs if you want to go to Crufts and bring your pooch with you.
Pavro and Distemper approx $40 each.
USA entry points do NOT recognize titers and you must show a Valid Rabies Certificate. And in the last couple of years when I travelled they did check out the Rabies certificates.
I suppose as a traveller you could get around this by getting a Nexus approval.
There is no rhyme nor reason to the newish regs at the border or any justification made for them. Do you Americans have a rabies epidemic down there?
Now there are dogs that for what ever reason the Rabies vaccine does not take My friend who owns a house in England wanted to take her dog with her - she did the Export titer and he did not pass. She had to leave him at home.