I just picked the 165000 out of the air. I thought it seamed like a reasonable retirement income for someone buying a $600,000 coach. I just punched that value into a savings withdrawal calculator and it turns out that based on a 3% return I would need 3000000 dollars in savings after buying my coach to be able to withdraw 165000 annually for 25 years.
I think most people with 3 1/2 million dollars in savings would have a hard time blowing 20% of their life"s savings on a rapidly depreciating asset such as an RV. And on the other hand I'm left wondering how many people driving $600,000 motorhomes actually have the RV paid for and 3 million in their savings account.
In the end I have come to realize that the posters here are right ... there is no rule; people just do what they feel like with their money and I guess it all works out somehow.