I was looking at RIP tour availability just this morning. I think you are right, they waited too long. Most dates are already sold out completely. The entire month of October is and there are a few dates available in September, but I'm sure opening weekend was, especially with the Media using RIP tour guides for house access. It's $339-$399 per person, plus the cost of the HHN ticket. I don't think they had tickets and just bailed, that's basically $1000 when you take into consideration that Jenn also had to purchase an event ticket, Tim should have one with his Premier pass, but he also said he was going to buy a Frequent Fear pass. And if they had it already booked, Manservant Mike would have just went in Jenn's place or Tim would have done the RIP solo.
I just know when they talked about it, when Jenn mentioned the going back to the hotel because, in case you didn't know, she's nursing that baby, she mentioned opening weekend and doing the RIP tour specifically. One of them screwed up.
Side note: the RIP tour is stupid expensive but it is 1000% worth it. We aren't "set for life" and that's how we do HHN.