There's always the old stand-by. It meets every one of your criteria, except maybe easy portability. There's a reason they call it a Beast. I have one with all three backs (8x10, 5x7, 4x5). It has reasonably inexpensive, relatively available accessories. It's so ugly the thing is endearing. And in case a nuclear weapon detonates in the same parking lot you can always crawl inside and be perfectly safe. (Yeah, it's robust...)

Calumet C1 8x10

As far as cost, I originally got mine along with two mounted G-Claron lenses (210 & 305), four working 8x10 film holders, Lee Filters foundation/compendium/filters, a brand new oversized Calumet blue/white dark cloth, and a large, very high quality cable release. Nothing was missing. Nothing was broken. Everything worked perfectly, but everything also needed cleaning. Total was $1,100 a few years back.