That’s why small and very small productions can start with Humble and GOG, where you don’t need to pay high fees but you do need to demonstrate quality of your product. If you are talking about EU countries with 50-65% tax, I guess you mean Nordics or maybe Netherlands. In Netherlands average salary €25,000 to €30,000 a year, so please tell me, how someone could spend at least half a year full time to develop a game, but can’t spend few thousand to publish it? Because it’s too risky and you don’t know if it sells? Well, this doesn’t sounds like you are working professionally as your first risk was not publishing but developing it for half a year, which already costs you x5-10 of the fee.
Let’s say fee is 5 000$, in one country this is an average yearly income and so it is a lot of money. But at the same time, your cost of living is low too - making 10 000$ in income from Steam (which is just few thousand units) gets you enough money for another year + fee for the next game. Sounds like a great deal to me.
In another country, where 5 000$ is about 1.5-2 monthly incomes, your problem is not a fee but a cost of living as you have to make 5 to 10 times more of that a year. At this point, your risk assessment should have be done long before you are ready to publish your game.
Btw, we should not use taxation or income levels of individuals as it applies only to hobbyists or amateurs. If you are a professional, which Steam customers are expect you to be, you already have a registered company and plenty of EU countries have tax deduction or other insensitive for game developers or just small businesses. You still will pay your personal taxes from salary that you pay yourself, but this is no different to other small businesses.