I agree 100%. If the visual impact does not come through online, then chances are there is nothing there in the original print to begin with. Still, for non gallery represented photographers, the internet is probably the best place or the only place to reach people. Galleries are limited in their reach but also in the number of artists they can represent. There is only so many prints they can market and try to maintain the highest prices possible. Since the split is usually 50/50, that is essential for both artist and director.
But for the size of jpeg files, with the spread of DSL and cable, the size of files can be increased so that detail is enhanced and loading speed maintained. I know The After Image gallery has increased the sizes of their files over the years. They also represent Brian. (a little plug ER?) Why not look around and right click some of the images and look at the properties for file sizes. That will give you a good idea.
But I like your idea of having framed prints hanging on the wall on a website. You just may have given me a project for the rest of the holiday.