I think you may be misinterpreting the studies. Generally speaking, there are very few people on the planet that are demoralized by being paid a lot.
Demoralization can happen when the social situation emphasizes pay as the only reward. The problem isn't that the pay is not an incentive, but the lack of social rewards acts as a disincentive.
If I tell you that I love the quality of the lemonade you are making for customers and I want to give you a raise so you will be happy to work longer hours making such great lemonade you will feel very appreciated and motivated.
If in the exact same situation I tell you that we need more lemonade and I know you don't want to work more but I am going to give you money so you need to do it, you are going to feel very differently. Its not that the money wouldn't have been an incentive, its that it is presented as if that is all you care about, which means your personal character and work ethic are being ignored. Very demoralizing.