The claim is sexist and it would be stronger without the wealthy-looking bit, but when building a dating site it's definitely the women that will matter. I think the OP's point (by analogy) is knowing which side of the market is constraining you and focusing on that.

For dating sites, men go where the women are and it's women who have more optionality, including not joining a dating site altogether. So if you're building one you have to think about what your women customers want first and foremost.