TLDR:
20€ = 2.300fg - 2.500fg
50€ = 5.750fg - 6.000fg
Looking for 20€ or 50€ Steam balance, using the ratio 1:100 USD:fg and consequent market conversion €:$ (1:1.15).
That is:
20€ = 2.300fg
50€ = 5.750fg
I can evaluate a margin for you not higher than 10%.