I wouldn't pay for BizE. I'd only pay Biz class prices on an airline where I could then upgrade to FC.

I'd never actually pay $5k to sit in a Biz class cabin.

Interesting, I was on DL 134 DUB-SNN-JFK a few days ago. There were 28 of us in the cabin. According to the manifest, 16 were NRSA, 10 were upgrades, and 2 were paid J.