These require you to use the card significantly, which comes with an extremely high opportunity cost. (valuepenguin.com)
Small gains in the education of teachers relative to other workers may not be evidence of declining quality, however; additional years of schooling may be more valuable for teachers because, as highly skilled workers, they face higher opportunity costs of staying out of the labor force. (educationnext.org)
While it doesn't have any annual fee, using the card comes at a very high opportunity cost, past the $ 40k mark because of other options. (valuepenguin.com)