Two economists have studied cashback mortgages.
A summary of their analysis is posted here:
https://voxeu.org/article/disclosure-sludges-and-cashback-mortgage-market
"Financial products with a cashback feature are increasingly popular, but typically cost consumers more in the long run. This column shows that consumers who are younger and less educated, and those affected by present bias and inattention, are more likely to choose more expensive 'cashback mortgages'. Advanced behaviourally informed disclosure improves consumer decision-making. Advertising in the form of a 'negative nudge' or sludge, however, encourages prospective buyers to choose more costly mortgages."
A summary of their analysis is posted here:
https://voxeu.org/article/disclosure-sludges-and-cashback-mortgage-market
"Financial products with a cashback feature are increasingly popular, but typically cost consumers more in the long run. This column shows that consumers who are younger and less educated, and those affected by present bias and inattention, are more likely to choose more expensive 'cashback mortgages'. Advanced behaviourally informed disclosure improves consumer decision-making. Advertising in the form of a 'negative nudge' or sludge, however, encourages prospective buyers to choose more costly mortgages."