Is spending big on pitching really necessary though? Just taking the two teams in the World Series right now and the starters they're using, they each have one elite-level salary in the rotation (20M+ AAV: Verlander, Wheeler), one pitcher with a mid-level free agent salary (10-20M AAV: McCullers, Nola), and the rest are pre-free agency/arb-eligible at best (sub-10M AAV: Valdez, Garcia, Urquidy, Suarez, Falter).
The Sox currently have an elite salary (Sale) and a handful of pre-free agency/arb-eligible guys (Pivetta, Whitlock, Bello). The mid-level free agent salary (10-20M AAV) guys are out there. They could re-sign Eovaldi and/or Wacha for that kind of money, just to throw out an example. That would put them on par with what the Astros and Phillies have done to get where they are.
Obviously, that they're not getting elite level performance from their elite salaried pitcher is a big problem, arguably their biggest. I'm not sure throwing big money after the problem is necessarily the best solution, at least not this winter with the current market. What they need is for their elitely paid pitcher to pitch like an elite pitcher, and for one or more of their cheaper options to make a leap. I know that's boring and perhaps futile, but I don't think spending money is going to be any more effective in the short term.