I am not following anyone of you guys tbh. But it might be that I am not familiar with UK tax law. When you are discussing net and gross income/salaries its the income tax you are referring to, right? Because that is at least how I have been taught to use those terms.
Is there not an applicable pay roll tax in the UK as well? In Sweden thats 31.42 percent, even if I know we are in the extreme.
In Sweden and most European contries it would be something like this;
Gross salary 200k
Net salary (after income tax): 120k (depending on the size of the income tax)
Total cost for the club: 200k * 1,3142 (using Swedish pay roll tax) = 262,84k per week total cost for the club.
Because many players ply an international trade they don't care about local tax laws so they negotiate a net salary. It's up to club to calculate the total gross salary and work out if it's affordable for them or not.
Sometimes players are paid in a foreign currency as well, like players playing in Qatar etc. often have their contracts negotiated in net US dollar terms, so they don't have to worry about shifting exchange rates.