It seems UA does charge a premium on the nonstop. According to ExpertFlyer, US has a $99ow base fare from SFO-MSY that allows routing via PHL, which is great from a mileage perspective (maybe not so much an operational one

)
Heck, it could even become MR-material.
Edit: Upon investigating, I discovered that it comes out to an excellent 3.3 cents per mile and therefore does make a great mileage run! You could hit Chairman's for a mere $3300.
US: SFO-MSY $240rt 3.3cpm