Your respondent level WTPs are metric variables like any other. However, because they are based on calculations involving division, they are more subject to outliers than would be a rating scale. As a result, I would probably NOT just subject them to a simple t-test like you learned in school. Instead I recommend one of two things:
You could conduct a median test using the point estimates - this is a non-parametric version of a t-test that's more appropriate to run when your distribution could include outliers.
You could also run a more Bayesian version of a t-test. This involves getting into the draws file but the test itself involves no more than counting. Please get in touch with me at firstname.lastname@example.org if you want more information about how to do this test.