David, to answer your question, the expensive 4x5 screen and the inexpensive 8x10 screen are the same; both come with an ultra-thin gridded GG/fresnel and a clear thicker plastic or plexiglass to cover the GG.
I'm not sure what the expensive 8x10 GG comprises, but the $80 version was more than satisfactory on my Toyo 810G.
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