Too bad it's me saying this, but I think you've made a heckuva point, especially that brilliant phrase, "temporary All-Star arm." That's Sale, Price, Beckett, Lackey, and a whole bunch of great arms who didn't pitch for the Sox.
There are of course significant exceptions--like Verlander--but that's the point: they are exceptions and absolutely not the rule.
I also like your notion that there is strength in numbers: that is, acquire pitching depth. I think that is exactly what has happen this season to the Sox lineup players, who constitute half the team. I call them the no-names, which really means underpaid. Casas, Wong, Abreu, Hamilton, and Duran are all @ $750K. Rafaela is $1.25M. That's 2/3 of the Sox starting lineup for $6M. The two big righty bats, Ref and O'Neill, are @ $1.85M and $5.85M. Lurking @ Worcester are Mayer, Teel, Anthony, and Campbell. Plus let's not forget that DFA'd Smith and McGuire definitely contributed to this Sox team.
I hasten to add that I think Devers ($30M) and Yoshida ($18.6M) are pretty close to earning their pay, but they are just two of 9.
The rotation started out like a house afire, and then stumbled badly after the ASG, but I think Houck, Bello, Crawford, Pivetta, and Criswell are right now borderline adequate. Including Pivetta @ $7.5M and Bello at $1.2M, their combined salaries are around $11.5M. And their WAR's are, in the same order, 3.4, 0.8, 1.6, 1.0, and 0.0.
Plus we also can't forget the failed (so far) investments of Giolito ($38M for 2 years, which are now 1), Story ($22M x 6 years?), and of course Sale, whom the Sox are paying $17M so he can star for the Braves. That's a whole lot of money for zippo performance.