If you have access to the needed equipment a straight axle isn't a complicated piece to make, so if you feel that is in your wheelhouse of ability then go for it.
I have dealt quite a bit with Ebay sellers, have yet to have any problems with companies who sell their products there, and only a couple problems in 200 transactions with individuals, only one of which couldn't be resolved. That $150 axle from EZBUCKET would get a real hard look from me(in fact it is very likely to end up under a project of mine, thanks for the link 57halfton
I hadn't found them yet ) and I do have the equipment needed to machine my own parts. That price seems very fair, and they are highly rated, with 100% feedback rating. I wouldn't be at all afraid to deal with them.