What does it mean that no one can ‘buy’ her beauty?

In Thomas Campion’s poem “There is a Garden in Her Face,” the woman he describes is so beautiful, he can only illustrate it using metaphors. Her skin in the color of a lily, her cheeks are “roses,” and her lips are cherries, which reveal her exquisite smile—teeth that are “pearls.”
Each stanza of the poem ends in a refrain that says no one can kiss her until she says “Cherry ripe.” This phrase indicates that the lady will only give herself to the suitor who is worthy of her when she decides she is ready. It could also mean that she doesn’t accept romantic invitations, but waits until she finds her perfect match.
Because she is a virtuous woman, she will not freely give her love to anyone who might desire it. When the speaker says no one can “buy” her, he means that no amount of coercion or flattery would cause her to give herself to someone if she was uninterested or not prepared to commit.