Hi Preethi,
Follow the below steps:
1. Create a measure to calculate total sales without affecting the filter
total sales = CALCULATE(SUM(Orders[Sales]),ALL(Orders))
2. Create a measure to calculate the % of sales vs total for that avg more than constant using below expression-
Column = CALCULATE(DIVIDE(SUM(Orders[Sales]),[total sales]),FILTER(Orders,AVERAGE(Orders[Sales])>2000))
Hope it helps you.