I have been self-employed under a Polish business (działalność gospodarcza) for the last few years. With income tax plus mandatory pension and health contributions, over a third of my income goes to taxes or other mandatory fees (like the requirement to have a licensed accountant keep your books). It really isn’t much different than most other EU countries. And of course one pays a comparable VAT on shopping.
Often in Poland people say “Why are you running your business here? Base it in Czech Republic!” The grass always is greener on the other side.
In Czech Republic as self-employed ("živnostník") your effective tax+insurance rate for income up to 2M CZK (~ 80k EUR) is never more than 15%. I have SW contractor friends paying around 8-12% - including health and social insurance. No need to have any accountant at all for income under 2M CZK, you just keep your invoices and sum your income at the end of a year, the tax return form is online and the sum of income is your only input.
Often in Poland people say “Why are you running your business here? Base it in Czech Republic!” The grass always is greener on the other side.