The only thing I can see that may hurt you is the super tech oil.. It's fine oil I know, and many people do, however many people that would opt for a $70 oil change will balk at super tech oil in my opinion even thought it may be better than the drum oil they have been using, but they just see a drum when looking at drum oil, or maybe a sticker it may say Mobil but may be conventional not M1.. That may be a hurdle for you..
I think 5 quart containers at walmart is going to turn out being the best buy, and it will be worth it to you chasing down oil deals for sure now at local parts stores.. keep an eye/ear out on sales paper, here in the forum etc. A name brand synthetic from the local walmart lowest price may be a good option.. worth a few bucks to show your customers (as you said) your putting quality oil in their engine. I wonder if you could strike up a deal with local parts store/stores if you buy in quantity ? If so it may still be hard to beat walmarts price, and I actually rather shop at walmart unless you run into the oil isle whack job trying to impress/educate you on which oil you SHOULD be using, you don't have to listen to the counter coo-coo at the parts store, and not to mention all the professionals in the parts store buying mirror dice etc.