Good afternoon.
The ferries are OK price-wise. They are not as cheap as CalMac here in Scotland. I am still in fits in laughter about the price they quoted me for the Western Isles tour. £ 42 for 8 ferries/13 hours. That's what I call value for money............
But the Norwegian ferries are not expensive.
Just so we are singing from the same hymn sheet (get our your maps now......), here is what I suggest to you from Trondheim:
Ferry from Flakk to Rørvik, bike over to Namsos and follow RV 17 (or just 17 or Kystriksveien as Multimap refers to it as) all the way to Bodo. You are passing the Polar Circle on the ferry between Kilboghamn and Jektvik.
You also need to bypass the long Svartisen tunnel with a local ferry between Vassdalsvik and Ornes.
The ferries are frequent, but research beforehand and take print outs and put them somewhere on your bike. The same as I do in Scotland.....
From Bodo, take the 5 hours ferry over to Moskenes (but learn the ferry times beforehand). The midnight ferry is less popular so go for that one. Remember; midnight = almost daylight. You can bike 24 hours a day. I once stood on guard duty in the army up there at midnight and it was 27 degrees warm. Bizarre........
Anyway; you are now in the Lofoten islands and you should be heading for Svolvaer unless you can swim. The road is OK. Not any hills worth mentioning. The tunnels can be bypassed. From Svolvaer, go to Fiskebol and take the ferry over to Melbu. Then head along the road and through some small towns to Andenes and the ferry over to Gryllefjord at Senja. Senja = Isle of Arran, landscape wise. It is Norway in miniature. Follow the small road north to Botnhamn and the ferry over to Brensholmen. From there, the road to Tromso.
From Tromso, one of the finest towns/cities in Europe, take the main road for 20 miles to Fagernes. Cross over and down to Breivikeidet, ferry over to Svensby, road over the frightening exposed Kjosen (remember to wear cycle helmet in case you get hit by a 100 tonnes boulder) to Lyngseidet, ferry over to Olderdalen and then E6 over the 400 meters/1200 feet above sea level mountain passes and then down to Alta, over the Sennalandet moor to Skaidi, the road over to Porsangen and then take over a small hill from Porsangen to Havoysund and then the coastal liner/catamaran over to Honningsvaag and the final, but very hard 35 km/20 miles to the North Cape where you get ripped off to the tune of £ 12 to get in there.
......Like tea in the park.