“How are you measuring your team's success today? … And have you ever compared that to anyone outside your own team?” (Almost always no.) “So the one thing you don't have, running it all with your own team, is anything to measure it against. You know your numbers, you don't know what they could be.”
“So here's what I'm suggesting: pass us some of your traffic. We run it right next to your team, and you only pay when we sell a package, and every package is a tour in your pipeline.” Don't size it for them; they might offer more than a slice. If they hesitate, THEN de-risk: “this can start small, even just your overflow.”
“If your team's already great, you got cheap incremental tours and proved them out. If not, you found out on a slice instead of betting the whole operation. Ninety days, and either way you know something you can't know today. There's no version where you come out behind.”
Then stop and let him react. The first objection means he's pricing it in his head. Handle it, then: “If you ran that, what's the first thing you'd want it to prove?”
Everything ends with “…and that generates more tours for you.” Tie every benefit back to more tours.