That's a pretty good one!!

I was doing some investigation awhile back and found a PDX-SLC-BOI-SLC-PDX that was easy to do in one day for about $100+ r.t. If you want to stretch it to 6 segments you could also do PDX-SEA-SLC-BOI-SLC-SEA-PDX.
(DL has an early morning PDX-SEA run and a late night SEA-PDX run used primarily for aircraft positioning)

DL is trying to compete with Herb's cheap PDX-BOI's nonstops but they have to do it thru SLC.

Any R.T. from a major west coast city to LAS is also pretty cheap but it would be pretty hard to get more than 4 segments per day.

Good luck, I'll make PM next week normally so won't have to rely on these runs.