Unfortunately no - the cost will depend on the number of visible pixels, and worse, there are secondary costs depending on the arrangement of those visible pixe

Unfortunately no - the cost will depend on the number of visible pixels, and worse, there are secondary costs depending on the arrangement of those visible pixels on screen, what part of the texture happens to be there, whether any sparse textures need to get paged in from system memory, whether GPU occlusion culling is going to cull certain things it wouldn't normally cull, etc. And other things are competing for GPU time like your OS compositor