Your 300k after tax is a guesstimate at best - are you saying they're being paid 600k+/week? LOL.
Many players have accepted slightly lower terms for the sake of their careers and moving to a 'bigger' club / league - it's certainly not impossible
Falcao at Moncao will be paying no / next to no income tax. So if he is on say £200k per week then his take home will be that...
If Woolwich offer £200k per week he will take home just over £100k.
Quite a considerable wage cut in real terms.