It's been mentioned many times on the forum that the value shown is only an estimate, and the actual final value is only calculated when you request the withdrawal.
The staff has never given a technical reason for using an estimate, but it may have to do with the fact that you can sell products before your tax interview is validated, and therefore, the final value is only calculated when you request a withdrawal.
From what I've seen, the estimate typically uses the highest tax withholding amount and assumes it should be applied to all sales. In other words, it's usually the "worst" scenario, and that's why you usually receive more than you expect in the estimate, but that won't necessarily always be the case.
Final user pay = Price + VAT (depend final user country) Developer payout = Price - Payment processor fees (depends) - Itch percent (normally 10%) - Tax withholding (depends)
Tax withholding is the more complex, The percentage depends on the country of the buyer and the country of the seller,
It can be anywhere from 0% to 30%, and is likely the main reason for the difference between the estimate and the actual final value.
You should also keep in mind that you may incur additional charges, such as the cost of validating the interview or charge backs, if applicable.