3300 euros is not enough, that obtaining a license and building in Estonia to start work is not expensive, I do not think that a company that wants to start seriously in the activity of encryption does not contain more than 1 bitcoin as founding liquidity.
Are there any legal documents, more restrictions, or just an increase in taxes?
The liquidity has nothing to do with the license's price. The license allows you to run your business and the liquidity indicates its capacity to pay its debts in the short term to pay suppliers, taxes, etc (it's also different from the solvability in accounting).
You can very well have less than 1 BTC (as your example)... if your company doesn't need much (companies don't have accountancy in BTC by the way)