I agree, but I would also expect to only receive text data and not images (or ve...

I agree, but I would also expect to only receive text data and not images (or very highly compressed images). The other part of keeping the bandwidth cost of an RSS feed down is keeping a smaller number of articles in "rotation".

EDIT: I just pulled their RSS feed - 50 articles currently in rotation! 32.42kB according to FireFox of just snippets of text and links!