Basically to make a sort of low profit on SF340 you have to charge pax EUR 100 per hour flown at somewhat reasonably good load factor.
Spot on.
Revenue required per passenger per hour, at a realistic load factor, and taking into account direct and indirect operating costs (and profit) illustrates perfectly why the 19-50 seat market is now so unattractive to manufacturers (Saab included).
If a 35 seat airliner is as uneconomic as you claim maybe you could explain how the DHC6-400 which only seats 19 has a healthy order book.
Much though I love the Twotter, classing it as an "airliner" is stretching things a bit - it has always been aimed at markets where its short-field performance is a bonus and/or its lack of pressurisation doesn't matter.