Well, that was a very recent change. But I don't know if that's very representative of Nordics in general, I know that shopping hours have been deregulated in Sweden for a quite long time.
Source: I went to Helsinki and forgot my camera charger. That's what they told me in the shop when I expressed shock that they wanted over €100 for a simple charger.
More recently, a couple of generations ago there might have been import tariffs on consumer electronics...?
I can't think any other tax on the product itself than the regular 24% value added tax. (Of course, the indirect ones, like income tax paid by employees, tax on corporate profit, etc probably show in the final price.)
Foodstuffs do have lower VAT rate (around 10%), so maybe the clerk was thinking about that, but that difference doesn't explain a 5€ -> 100€ hike. Maybe you just managed to wander to the most expensive retail store in the downtown and had an unusual camera model...
Finland is expensive place, but most of that caused by more mundane reasons than special "luxury tax", like indirect taxes, regulation, and shipping costs raising the general price levels.
Nonsense.
Also, store opening times are nowadays unregulated in Finland.