It was split amongst two guys, but the Rams had nearly $45M in cap space or 24.5% of the cap dedicated to the QB position last season. So its been done
Not really responding to you specifically here, more in general, but I really dislike the idea of only looking at the teams to actually win the Super Bowl as being the models that need to be followed for building a team. Sure, that's the ultimate goal, but any of 3-6 teams any given year are right there at the end and built for winning even if they don't win. Were the Bills, Bengals, or Bucs not capable of winning it all last year with however their rosters were built? I don't know how many further examples there are of teams with 20% or more of their cap spent on a QB that were Super Bowl quality, its probably kind of a moving target, but that's the type of team I want to build with the Ravens. Be in that top group of a handful or so of teams that have a legit chance as often as possible. I don't care about specifically emulating whichever team actually won it all.
Do you think the goal post should be the conference championship? Making it to the super bowl?