Use the self sign option. I haven't had any problem having products
accepted on the Exchange with a self-signed job.
I would be very interested in how you create your file for uploading. Online? Adobe Exchange Packager? My files work on my machine every time. But when I upload The Vetting Team fails them EVERY time. I have been trying for weeks...
I haven't done this for a while (around a year), but when I did, I used
the free Exchange Packager and it passed the vetting.
It's not impossible that they've tightened things up and now actually
insist on a proper digital signature. But in any case, did they not tell
you why they failed it? I recall that they do give a reason.
Also, I think a digital signature is more like $100 a year -- not as
much as $1000. (Still a waste of money though!)
... however, I was just packaging a single script file -- not using CEP.
I have followed the way of coding described by Olav Martin Kvern.
It is kind the new way of writing extensions. But I am not sure there is exactly a Tsunami of extension coming our way...
Personally, until it's very clear where things are heading, I'm sticking
to regular scripts with ScriptUI. Why limit your market to the latest
versions of InDesign!