SuperStall - you can go by bus from PIK to anywhere in Glasgow for 50p; or alternatively anywhere in Scotland by rail for 50% off (free if it's in the first year of a new route). Journey time by rail from PIK to Glasgow Central is around 45 minutes and fare is £2.50.
That's a lot cheaper - and not a whole lot slower - than coming in from Abbostinch (which isn't exactly a city centre airport!)
So, even factoring in the time - BA is
still over £150 more expensive!!
BTW, the cheapest I've flown on FR PIK-STN was 50p and as I think I've said elsewhere more usually I've paid £4.50. Don't
ever think I've seen BA fares like those!