Interesting, did you take these from a calculator? I'd love to see a graph of the marginal tax rate from 1k till say 6k.
Because here it seems from 2k, 3k or 4k, an extra 600 is taxed consistently by more than 50%, and sometimes even 75%. That's a very high marginal tax rate. I wonder if that's cherrypicking something and the x600 to x000 range looks better.
I also wonder what the taxes break down into, I think it's always good to separate pure taxes (going to the government for the public good) from various social safety net contributions (some of which go to a general fund for the public good, but some are also individually-accrued benefits by paying a monthly premium, e.g. unemployment insurance of your particular salary).
When making cross-country comparisons, I find there's a ton of apples to oranges comparisons like this, where taxes and other things aren't properly separated and just lumped together.
Another example: in some countries healthcare is arranged as a benefit on-top of gross income. In others healthcare is subsidised by 80% by the government, and paid for through a tax on gross income. It could very well be that compensation in both these countries is the same, but that the former looks like you're earning more because you get paid out more of your gross income.