costco aren't doing this offer, they are doing £50 off 4, effectivly the same...
for what its worth iv'e had the ps2 tyres on my d5 and got around 3-4k on the fronts...
amazing grip mind.
ps3 is supposed to be better, but i'd go for the primacy's, jsut got my second s60, came with 4 Pirelli P6000 (all decent tread), recently swapped to primacy and the car just feels awesome
out of interested what place you getting thos prices from? I just swapped all 4 on mine 225/45/17 primacy for £111 each fitted!