Guess you are a moron who drives a vauxhall with your blindfold on
Probably because they are not Isize and their is not a list of compatible pushchair adapters. If not going for Isize the maxi cosi cabriofix or the Britax infant seat are often on offer for under £100 those ones have scored well in crash tests. A better indicator of quality than price
U need a base for these at £175
When you can see it is made of better materials that are sturdier, with better harnesses and side protection padding then yes it is going to be safer. I have seen some of the rubbish pedalled at Halfords, TRU and Mothercare for £30 to £70. The Audi tax on these at RRP is likely to be a 30% markup over other well established equivalents by Recaro, Britax etc. There is no way Audi are selling a £50 RRP car seat for £250 because they added their badge. At £100 these will almost certainly be a good buy against other makes which are selling at around £180.
Just because you are buying a more expensive seat doesn't mean its safer. You're a marketing departments dream...