it is still getting paid for, just via tithing (and maybe other Church business endeavors?). It is not as if BYU has found some magic elixir to provide top-notch college education for pennies on the dollar. Clearly the Church views the opportunity costs of giving a cheap education to the top students within the LDS population as favorable (otherwise they wouldn't do it), but to say that it somehow costs less is a bit disingenuous. Even on their own website (https://admissions.byu.edu/how-much-does-it-cost) they tout the low cost of tuition and clearly state that were there not the tithing-funded subsidy that its cost would be on par to the student of $29K as compared to other sister private institutions.