I have seen 4 t6XAS 75 mhz radio systems on ebay in the past year or so. I bought one for about $120 inc shipping. My buddy bought a better one for less. I recommended one on this discussion group and noticed it was "buy it now"ed the next day for about $175. Might have been coincidence to my posting. I saw another one a couple months ago. So keep looking.
Not a lot of grd freq systems on ebay, but now and then they are there for a bargain price - failed battle bot/robot projects. But lots of them on 72 and 50. The 50's seem to go especially cheaply. There have been 2 in the last month as I remember. If you just have to have a 6xas, you can get the radio converted to 75 mhz by who?
www.radiosouthrc.com futaba tower hobbies
Cost is what? $50 to $100?
Of course, for a bit over $100 total you probably can get a 7 or 8 channel with 72 mhz module on ebay. You can reasearch it on the "futaba manuals" site and find out which ones have modules. Then get the proper 75 mhz module from one of various sources. Radio South, maybe Tower. About $50. Of course that is not a 6xas (which really are outstanding radios), but it can be a fairly nice PCM computer radio. A lot of them are a bit old and beat up, tho.
If you or anyone cares, these are the radios that have modules:
7uap 7uaps 7uhfs 7uhf 7uhp 7uhps 8uap 8uaps 8uhf 8uhfs 8uhp 8uhps 7uaf 7uafs 8uaf 8uafs. You can cut and paste in the ebay search - "any of these items".
If you get a radio converted from 72 to 75 mhz you need to think about getting or converting a receiver as well.
You have to get creative searching for t6xas radios on ebay - search for whatever the seller might mistakenly call his radio. They are listed as 6xas and t6xas of course, but other names too sometimes. The best thing is to just search "Futaba" in a price range. That way you might find a 6xas that most people are going to miss "6txas" or whatever.
Scott