Std. Price change in MMR

Hi.

We Purchased a material ABC from vendor and sell it to our customer. We wanted to change its Standard Price in Material Master Record.

Current price is 20 wanted to make it 50.

When trying to change it from MR21, system is showing "New Price" field is disabled for material ABC.

But for others materials "New Price" field is enable

MR21 is correct place to change the standard price for purchased material ?

is there any cuztomizing setting to enable a "new price" field ?

Appriciate your early response

Thanks

TL