salary cost to the company is a lot higher than gross salary (which itself is a lot higher than net salary). you can guestimate total salary cost to be about 1.5x gross salary, so for the lower bound: 100k / 1.5 = $66,666.67 = €57,813.34.

€57-114k p.a. is well within the order of magnitude of yearly gross developer salaries in Western Europe (e.g. Germany).