First off, the MK23 and the Tactical are 2 different guns.
The MK23 is the BIG one and goes for the $2k you mentioned. The Tactical is a little smaller and goes for about $900.
I have a Tactical. Both have a threaded barrel (in opposite directions), but the MK23 (aka SOCOM) is longer. The SOCOM also has a separate decocker, where the Tac is integral to the safety. Both are .45 ACP, and come with a padded case and accessories. There are a few other minor differences between them.
The MK23 is too big and heavy IMHO, especially if you attach a can. I much prefer the Tac. It costs less than half the money and is a great pistol.
I don't have huge hands so the Mk.23 usually sits in the safe. IMHO the Mk.23 was designed to be an offensive pistol not defensive. For all-round shootability the Tactical is a better choice. If you want a Desert Eagle sized .45 thats the Mk.23!
I've only seen one SOCOM Huge might be an slight exaggeration, but it is big...bigger than a USP 45 which many view as "big & bulky" to begin with.
Personally, I'd go w/ 2 Tacticals @ $900 each and still save a few hundred over a single SOCOM.
In a pinch, I've successfully concealed my USP45 IWB while my usual carry piece was at the shop.
If you wanna save even more $$$, buy yourself a standard USP45 for around $650, or even less used (I see lots of 'em for sale here and at www.hkpro.com ) Then purchase the tactical barrel from CFI for around $185 (again, seen 'em used on BB's).
Of course, that will leave you without the "match trigger" and the extra tall sights, but other than "Tactical" stamped on the side, those are the only other differences.