I went to Norway 3 summers ago camping with my brother. We flew to Bergen, got the train to Voss, camped there and then went around Hardangerfjord and back to Bergen, stopping off at campsites on the way. Campsites in general were cheaper or comparable to those in the UK and had similar levels of facilities, if not slightly better for the price. The difference there is they were all on fjord edges.
You can get around easily in summer because the public transport works, i.e. connecting services wait for one another. Also the express boats, whilst not cheap are reliable and you get to zip about stunning fjords at a decent price. If they are too busy you sometimes end up with a free journey anyway as the ticket vendor can't get around fast enough. One thing to keep in mind is the boats are half price for students and buses offer a big discount too. Students for that purpose = anybody with an ID card with something educational related on it. I saw people using work passes and I had a college ID card about to expire (no NUS card).
If you are camping, really the only thing that is particularly expensive to buy is meat, bread rolls (but not loaves) and beer. Yoghurt, cheese, loaves, nuts and basic foods were about the same as a UK city. Obviously bars and cafes are pricey but we didn't go in them. If you really have to have alcohol, cans in the shops ranged from £3.50-£5.00. Hardangerfjord is a fruit and cider apple growing region and large punnets of fantastic berries can be had for prices that put UK prices to shame.
The Tall Ships festival in Bergen really is a thing to visit, hoping to see it in Alesund sometime, too. The only time we bought anything pricey was beer in Bergen at the end where we were spending £8 a can on beer and £100 on substandard accommodation because it was Tall Ships weekend (I left it till the last minute as I didn't even know it was on). Even with that we spent £300 each in total for the week.