Alpha3d, I don't get your point.
The cases where you just get 60% of the price might be when there is a VAT of around 20% applied for EU customers (you can verify on your sales list).
If so, these 20% don't go to CGTrader but to the EU countries. So don't blame them for respecting the law !
You should be glad that CGTrader takes care of this for you, otherwise, you would have to identify from which EU country your product was bought, and you would have to repay the VAT manually, which would be a real pain. Of course, you could choose to ignore this VAT, but that would be illegal - with the possible consequences.
Just because of the royalty rate, this year, I already made more money here than on Turbosquid, despite of a higher number of sales there, and I don't have to care about tax issues : believe me, on CGTrader, you're not ripped off by the team, it's even the exact contrary.