What is revenue share in a search feed?
Revenue share is the percentage of each ad click's price that is passed down the chain. The search engine keeps part and pays the rest to its partner. If that partner is a feed provider, it keeps a further cut before paying you. Terms are negotiated privately and vary with volume, traffic quality and whether you hold the feed directly.
The only widely cited public figure is old: in 2010 Google disclosed that standard AdSense for search publishers received 51% of what advertisers paid. Large syndication contracts are negotiated individually and are confidential, so treat any specific percentage you read about arbitrage feeds as unverified.
What you can verify is your own take rate chain. A hosted feed from a feed provider carries two shares, the engine's and the provider's. A direct feed removes the second, but brings compliance duties and minimum volumes. A higher revenue share is not always better: a provider with a lower share but better coverage, faster payment and fewer deductions can leave you with more.