I checked the free agents I signed recently, and also double checked the total fee paid today by my L12 team against its income & Expenses Statement. There seems no abnormality except wages, so as the transfer fee, of one of the free agents I signed today is exceptionally low.

Probably my server is different on this. Or my teams' levels are still too low (12 & 20)

If they charge 40%, that's unreasonable. If they charge 10%, this can at least be explained as matching the re-signing fee.