For people who are starting their journey in GUM, this is a perfectly reasonable thing to do; the fares are set up to allow routing on the hopper; there are a high number of permitted transfers, and the route table allows the hopper cities. Everyone else is likely to see the price skyrocket when they try this, as most discount fares are not routable through MAJ, KWA, etc.

That said, for people who are intending to take the eastbound hopper, one approach might be to find award space to GUM and then start your paid ticket there.