I really do hate when prices in a store or website are not what ring up at the cash register and I as a consumer do not calculate my total each and every time, in good faith I trust that the restaurant/retail establishment has the correct pricing. Stores like Walmart even have policies around giving refunds or discounts for items that ring up incorrectly at the register. Usually if I notice a discrepancy or am genuinely unhappy shopping at a store/restaurant I will not return, I vote with my $$.
All of that said, this professor is a grade A moron. He can take all of those fancy degrees and shove them sideways where the sun don't shine. In the past I owned my own business for 7 years and 99.875% of my customers were great. I ended up not being paid by 1 person out of tens of thousands of services provided. I lost 1 customer during that time, guess what? He was a lawyer. IMHO, many lawyers like to control everything and when they cannot they resort to acting like big shots. My customer was mad because he requested that his lawn be sprayed for weeds while I was mowing his lawn on a Friday afternoon. I explained that since I had just mowed that the surface area of the weeds would not be sufficient to provide adequate results and thus a waste of time and money. I told him I would return the next Wed to spray, he was fine with that. Monday, Tuesday, and Wed it rained buckets and my schedule was all messed up. I returned the next Friday to mow and was approached by the same lawyer, keep in mind that I almost never dealt with him. I always dealt with his incredibly nice wife who loved me and knew my kids names and birthdays. He asked why I didn't spray the weeds on Wed like we discussed. I asked him if he remembered all of the rain earlier in the week. Him - I don't care, I want the weeds gone. Me, Yes Sir, I do too and I will get them next week. Him- not acceptable Me- it is against the law to spray herbicides in the state of VA while it is raining due to runoff possibility. Him, don't care I want the weeds gone. Me-so you want me to knowingly break the law? His wife was standing about 20 feet away. Neither of us raised our voices, but she was crying and I knew why. Because she had seen it before, her husband being a jackwagon. I picked up my stuff and left his property at this point and never returned, he paid the final invoice.