Your purported knowledge of the church's financials is suspect, at best. How exactly do you know what the church's cost structure looks like? The church used to disclose its financials. It hasn't done so in decades (see the 1950's). My friends who are employed by the church's financial arms claim no one person sees all of the financials. I'm impressed that you feel comfortable drawing conclusions on what presumably is incomplete information. If you somehow do have access to complete information, it is highly confidential, and I'd be shocked if you'd be so casual in sharing tidbits in a forum like this.
Notwithstanding just how suspect your knowledge of the church's expenses may be, it is somewhat contradictory to state that education is one of the largest expenses 'outside of the largest expenses'. Huh? So other than the largest expenses, education is a big one. So is it, or isn't it a large expense? You don't seem convinced yourself.
And hold on, we're not even talking about education, right? We're talking about athletics, which is I understand to be self sustaining and not a drain at all on church funds*.
You go on to assert that if anyone understands economics principles such as MU = MC, it's the church. When, exactly, did the church and its religious leaders become economics professors, or the leading global business decision makers? You must have forgotten the long history of economic decisions beginning with the Kirtland Safety Society (failed bank inspired by revelation) continuing to the RE investments under President McKay in the 50's and 60's. Of course, since the church has since ceased disclosing financials, it's tough to see just how much it has improved in recent decades. But rest assured, the only record we have is far from blemish free. It's an interesting assumption to make that the church knows best, unless you just boiling it down to spiritual matters.
Lastly, why should any of us care what you'd be comfortable with in terms of church expenditures? Do you have any credentials for us to care about at all? Or is your hesitation to support athletics more just a 'gut feeling' that we're already doing enough by not investing one red cent*?
(*my assumption is based on articles suggesting that BYU athletics is 100% self funded, and is not a drain on any church revenues. My assumption could be wrong, and I'd love the church to disclose details and prove me wrong.)