First,
I am truly sorry you have a problem. But things can and do happen that none of us want.

Second, That 300.00 plasma cutter off of ebay isn't likely to even function once
Third, anytime you let anything sit up with mechanical relays, they are subject to stick, or not work.
Would you expect to take a brand new car, drive it once, and then promptly let it sit for 5 years and expect it to start when you turned the key? Keep perspective. You are being unfair in your assessment (in my opinion). You'd be just as likely to fair the same with any other brand due to similar manufacturing components and materials. Being disappointed in a product that was neglected and not used well beyond the warranty date is simply a bit over reaction to me. I know you spent money on it, but you'll find plenty of threads (if you do some simple research) where name brand X failed right after the warranty was over, for whatever reason. I've read numbers of threads over the years myself where the name brand failed even though it wasn't used after sitting three or four years.

FWIW, the lack of the amp cutting back to register the pilot arc means that a relay is likely stuck on the board. Any decent local electronics guy can trace it down and replace or repair it. Switch it over to continuous rather than tip saver start and test again and see if pilot arc amperage doesn't drop down to 24 amps or so.