Mood swings of ethical behavior - a personal experience

How does a person's ethical perspective change with the sequence of events that occur regarding a particular issue? This question was clearly answered few months back when I was purchasing a camera for my sister. It was a day before Black Friday and I was skimming through all the store brochures to find the best deal for a digital camera with the latest technology. I finally concurred upon a Nikon S51 and the best offer was @ Circuit City for $210. So, we, my uncle and I, went at around 4 in the morning to Circuit City, stood in the line outside the store at freezing conditions until they opened the store at 5am. We rushed in at 5 to the camera line and then stood there for another 2 hours to finally get the chance to buy a camera, and the only option we had at that point was a pink Nikon. So, we purchased it and just headed out to the mall for a more simpler and casual shopping.
While we were window shopping at the mall we just happened to enter this camera store called Ritz Camera. In that store the same camera in an attractive chocolate brown color was available for a surprising $99 only. We were shocked by this offer, initially, but then later we got excited about it and then, thanks to the return policy of all stores in the US, we bought it using my uncle's credit card. At first, we thought only that particular salesman was misled and was selling it at such a low price, but we did confirm with others that he had been selling the cameras at the same price to others since morning. But later when we got back home, we did feel a bit guilty about buying it at such a lower price and actually were thinking about calling the store owner and reporting this issue. Surprisingly, the store owner calls up my uncle and tells him that she will directly charge the extra $150 and doesn't even attempt to apologize for their mistake. This move actually got my uncle very aggravated and he retaliated by directly contacting his credit card company and commanding them to block this new transaction. My uncle felt that what the store owner did was so unethical, that he ended up changing his mind from returning the camera to fighting with them and keeping the camera.