Walter stops by to see Jesse. Reminiscing about the start of their partnership, they cannot help but wonder about sticking with the old recreational vehicle (RV) even when there was enough to replace it. While the RV served them well in their first attempts to cook methamphetamine, the two did not upgrade until they started working for Gus Fring. The ownership/endowment effect underlines the scenario in which some people are unwilling to exchange something that they possess for the same amount of money that they would pay for it (if not owning it). Walter and Jesse loved the RV even though it had, and brought them, many problems. From a rationality standpoint, they may have been too concerned with the sunk costs that they have incurred.
See more: cost benefit analysis, opportunity cost, rationality, status quo bias, sunk cost
The Economics of Breaking Bad 