I've bought from various private sellers on Ebay when they were destashing. Got some great deals, but you can't count on there being fabrics you might be interested in there unless you buy from one of the commercial places that sells on Ebay and then I think you're going to pay about the same as if you'd bought from either an on-line store like MSQC or Connecting Threads.
Probably will jinx myself, but I have had mine since 2010 (7700 Horizon Red) and not had one bit of problems.
I too had a 7700 JNH and had to send it back due to it just dying on me after 3 months. One day the LCD went black and then the machine just died. The only reason I got the 7700 was because I ordered it online and at the time, they could only offer me the 7700 and not the 8900 to to policy. Because my machine was brand new. my dealer gave me full credit for my 7700 and for an extra $500 made an exception and replaced it with a new 8900 Horizon. BTW, Janome retired the 7700. You were not only one to have issues, unfortunately. Personally, I would think about upgrading to a 8900 Horizon as the difference between the 7700 and 8900 is day and night better.