In sales process condition type VPRS is the cost of the material. This statistical condition type could take the value from MMR i.e. MM02/3 from field "Moving price" or "Standard price", Tab Accounting1.
Furthermore with AltCal Type 11,in the pricing procedure, the profit is calculated in the sales order by subtracting VPRS from Net value.
When Pamela talks about pricing is she referring to VPRS or to PR00 (if we take standard SAP SD terminology)?
If I have not understood your post, then please explain it.
"So I think the system may not allow since tax condition type/VPRS is compulsory? is it ?"
A condition type could be made mandatory (or optional) in the pricing procedure (V/08), field "Required".
Please explain your process again and more clearly.
Also read the post by Sridharan. It is a good post.