105 per corner fook that is that for 16'' s? I have paid just 200 for all 4x 195 50 15's 2-3 yrs ago and not that much over 200 last time also, shop around!
Prices haven't really changed much 195/50/15 still remain to be one of the cheapest "sporty" sizes available due to it's mass market use. £30-£40 a corner isn't unknown for a decent brand tyres wheras 16" 195/45 or 205/45 can be double that often. Plus 16" tyres have always been relatively expensive compared to 17" and 18" tyres (ie not much cheaper in some cases).
To the OP, if your rear tyres have a lot of tread left I'd get a new pair of PE2s, nothing worse than a car with mixed tyres. Plus they probably are the better all round tyre and also the geniune oe tyre.