I am only paid half of my sales by envato.

I have sold around $100 in codecanyon but i am only paid half of it. What could be the reason beyond deduction.

Envato fees and taxes esp. if you have filled out a W8 form

@mgscoder is better at breaking it down than me but it makes sense at a basic level.

in your screenshot we can see there is no US backup withholding tax deducted. So, in your total item price there are:
( ( Item Price - Buyer fee ) - TAX ) - Author fee = Your Earning

for html category Buyer fee $3.

Check your Author fee here:

Hope now you will be bale to calculate your earning.