No, they're not, they're additional factors to be considered in determining the value of the tickets to you, as compared to the value of the $500 you could get for them. The article ignores such factors, presumably for simplicity of exposition, but that doesn't mean they're not relevant. The correct rule is still to ignore sunk costs, because those are in the past; but the correct rule by no means says you should ignore relevant future impacts of your choice (like your spouse being upset because you sold the concert tickets) just because they aren't monetary.
No, they're not, they're additional factors to be considered in determining the value of the tickets to you, as compared to the value of the $500 you could get for them. The article ignores such factors, presumably for simplicity of exposition, but that doesn't mean they're not relevant. The correct rule is still to ignore sunk costs, because those are in the past; but the correct rule by no means says you should ignore relevant future impacts of your choice (like your spouse being upset because you sold the concert tickets) just because they aren't monetary.