I don't think of E6 film and development as driving anyone bankrupt. Sure... not cheap. But developed in your Jobo? Not the worst thing I could do by any means. I think I find E100 in 35mm gives me pause, but less so in 4X5 because you tend to be more sparse in shooting it? My estimate is close to 3X B&W in 4X5.
FWIW, 4X5 is far easier to get into development without having to fuss around with wrapping, threading, and wrestling it onto reels. One thing kind of weird (using Arista E6 chem) is that the initial water bath with 35mm is green/blue while with 4X5 it runs pink. Freaked me out a bit at first, but it came out. Since this was my first time doing slides, I have to say I wasn't prepared for the way the films dries. Initially, you get images on one side and cloudy "mud" on the other. But after an hour or so, the "mud" dries clear and you're fine. Having seen this and been put off each time - three times in a row, I'm getting used to it. If you go this route, just be forewarned and man up.