Though I didn't look at every tablet on there, I took a peek at the most expensive ones. Based on a quick glance, in general most of those:
- Have a slower processor than the Galaxy (which is clocked a 1 GHz)
- Have less RAM than the Galaxy (which has 512 MB).
- Don't support cellular data bands (3G/WiMax/LTE/etc), so they only have WiFi chips.
- Have a fair bit less internal storage. The Galaxy is available with 16GB, and I believe there's a 32GB model as well; the largest I saw on your linked page was 4GB. Both the Galaxy and most (if not all) of those also support up to 32GB microSDHC cards, so a Galaxy could potentially support up to 64GB of total space.
- Some of them don't appear to have cameras. The Galaxy has a back camera at 3.0 MP, and I believe it has a front one as well (not positive on that).
And of course they're running an older version of Android. Whether it's worth the price difference...well, that's an individual choice. That's a fairly broad overview of some technical differences, though.
Some Galaxy specs from Samsung here.
And specs on Wikipedia here.