Rear Sportmax Qualifier D209.... Ouch!

So, I was getting a little concerned: rear tyre pressure should be 42psi. Checked it, 30 pumped it up. 24 hours later it's down again.
Now, forgetting the childish guffaws from the back from anyone who thinks a tyre that keeps going down on you is funny, the slow loss of pressure was becoming a concern and you couldn't be sure it was safe.
I suspected a valve or the outside possibility that the tyre wasn't seated properly on the six-inch rim.
Anyway, a quick trip to my local branch of Laguna Motorcycles informed me it had a tiny hole.
"No we wouldn't recommend repairing it sir, a new one is £143."
Bugger...
And then two minutes later the fella (he wasn't a mechanic, he was 'technician') called back and told me the 200 section rear tyre on B-King is special and "...that's £173" (and he was right it's got NK on the end though I'm unsure why the one used on the ZX12 isn't ok)
The news spoilt my weekend I can tell you.
And, they had to order it in and it won't be ready for three days so I left it there.
Interestingly, I could tell the tyre was going down (stop giggling) and despite my relative inexperience with this hefty machine, it still handled ok.
So, while I spend the next two days worrying that those nice technicians will be 'test riding' the BK in their workshop **, I'm thinking:
A. I really could have bought it cheaper on the 'net, but by the time I take into account travelling, getting someone to fit it etc etc, that £173 is no TOO bad.
B. How come Maxxis can knock out a pair of Tyres for the BK at £135 and how much crappier can they really be?
The Sportmax seems to be the best there is for the moment, but anyone out there have any suggestions?
(Yep, I know, safety, OE, best there is at the moment etc etc)

** Note added Tuesday May 19 2009. Actually having just collected the bike, they've done a good job. Laguna on Ellingham Ind Est in Ashford. Nice blokes, nice enough shop too, and they looked after the bike well.

Couple of points:
Sportmax Qualifier D209 200/55 17. Speed rating W... which Dunlop says can't be repaired, no matter how tiny the hole (interestingly I picked up the old tyre and it was really light, only a few pounds, certainly a lot less than most tyres I'm used to lugging around off of old middleweights. That'll be progress then, eh?)