My take, on those flight segments, not worth it to pay that much for upgrade from W to F.
Someone once posted the rule of $1 per minute is a rough rule of thumb on whether or not to pay the upgrade.
You get a slightly larger seat, maybe a PDB, probably a second round of beverage service/re-fill, and a slightly more enhanced snack basket, and of course more the EQM bonus.
I'll buy-up on longer segments that are 2+ hours in flight, but not the short stuff.