Can I only pay for revenue enrichments when companies actually return revenue data instead of paying for failed enrichments?

No, Clay currently doesn't support paying only for successful revenue enrichments. Data providers don't allow Clay to pull single data points like revenue - they require requesting and paying for the full enrichment each time, even if the specific revenue data isn't returned. You can use conditional runs to limit enrichments to companies that meet certain criteria beforehand, but you'll still pay credits whenever a provider returns any data, regardless of whether it includes the revenue information you're seeking.