I live in North Wales.
Being a resident and a walker in this beautiful area a set of good maps are prerequisite.
I prefer the laminated OS Explorer series. OL17 covers most of the Conwy valley and all of the Carneddau and the Snowdon massif. It does this admirably by covering it on a double sided map.
Despite on the usual grumbles about this sort of map, (i.e. you always have to turn it over for the bit you want or the area that I want is in the overlap of the two maps, etc.), for me and I daresay many others it represents very good value for money in that a double sided map such as OL17 costs exactly the same as a single sided map, about £14.00 if I remember correctly.
I want to explore further afield. My intent in the summer is to do a bit of walking around the Lleyn Peninsula. The maps for this area are not in the OL Series, but are covered by OS253 and OS254. The problem is, because I will have to purchase two maps this will cost nearly £28.00 for the laminated versions!
The area covered by the two maps is probably less than the total area covered by OL17 for Snowdon and the surrounding area, but Ordnance Survey, for some reason have decided that they didn't want to cover the whole of the Lleyn Peninsula on a double sided map at a cost to the customer of a more reasonable £14.00.
Although half of the price of the double sided map would probably be too much to ask for, I would have thought that the single sided map price could have been pitched at a more reasonable figure, perhaps just a little over half the cost of of what they are actually asking. So if you want to buy both maps the cost isn't so blatantly astronomic and at least reflects a comparison to the double sided maps that are a available.
There must be other areas of the UK that other people have had the same complaint. I've registered my complaint with Ordnance Survey but they totally dismissed me. Its a pity that they seem to have the monopoly on detailed mapping in the UK, if there were some genuine competition, they might think about their pricing a little more!
It would be interesting to find out what your views are.