Yeah, that's a lot for license costs, but in my country (Finland) they are in some places even more expensive, so I am kinda used to that. I think beginning of May is good as well for Slovenia, and not very crowded. I was there once in the end of June, and it was full of tourists. Rafters...
That is actually true. Kind of forgot to mention this in the article. I think the prices per day were something like this:
Idrijca trophy: 90€
Idrijca B: 60€
Sava Bohinjka: 45 - 59€
Upper Soca & Lepena: 59€
Licenses are definitely the most expensive part if you stay there for longer...
I wrote a blog post about our May 2018 fly fishing trip to Slovenia (Idrijca, Sava Bohinjka, Soca, Lepena, Unica). Feel free to read and motivate yourself for a trip! :)
Slovenia Fly Fishing Trip - May 2018 - Mercury Fly Fishing Blog