Hello,
The effective price is calculated automatically by SAP based on the net price and the other conditions you have entered (including discounts, freight etc).
The conditions entered in the conditions tab are basically supplements to the net price condition. Go to M/06 with your net price condition (from your screenshot it appears to be PB00) and check the pricing procedure assigned to this condition type in the Master data section.
Now go to M/08 and check where subtotal 'S' - Effective price is assigned in this pricing procedure. This should tell you in which order your conditions pile on.
If you do not have a pricing procedure assigned which might very well be the case, this is the reason for not getting the correct effective price. Please run report RM06PIN0 following these notes:
392988 - Consulting: Prices in info record and RM06INP0