In Poland the government is in on it when it comes to specialists of any kind, as this is how they prevent people from emigrating to the west or "emigrating" (tax-wise only) to the Czech Republic, which offers a similar deal.

For a while it was possible to have a flat 5% income tax rate, but I guess someone pointed out that it's too generous, so the best option now is a flat 12% and 3% healthcare contributions.