I think you are totally correct that su does this to verify season tix pricing, the $70 does roughly equate to the tix cost per game there over 7 games.
But still, as you said, I dont think many of us would have a problem if, say, 10 days before a game vs a MAC school no name (for casuals), su dropped 20 or 25 bucks off singles that didnt sell as a season tix. Just so non diehards (which we need 7 or 8k of to sell out any game), would actually buy them, and take their family.
Im happy to pay more for my tix than casual fans, its a price I for one would be more than willing to pay (yes, pun) to get the Dome filled. Personally, a full house enhances my gameday experience exponentially.