There are ways to get an A/C TIG for a bit less if you don't mind older equipment..

Hunt around for an old Miller or Airco Heliarc box.. You can find em for $250-$300 sometimes.

I had a 1957 Miller TA-252BP TIG AC tig welder.. great unit but it's the size of a refrigirator.
It ran 10-400amps.. single phase 220v with PF caps. remote foot control and gas/water valves with post flow timer..
I have pics of it here
http://www.pontiacs.org/modules.php?...view_album.php
I has to sell it when I moved to CO.. The company wouldn't pay to ship it.

They turn up on Ebay from time to time.. also watch local equipment auctions.
There's always a welder or two on the block.

Uh yeah.. Don't get a 3 phase unless you have 3 phase power.. phase converters don't work well on welders.

Anything over $500 and I'd spend the extra $$ on a nice light inverter model.