If you have 15 friends that are all willing to chip in and help with the cost, I have found what I believe is one of if not the most expensive Airbnb's in Illinois. It's a Spanish-style villa that has its own basketball court and movie theater, too.
How do you feel about squirrels? The reason I ask is there's a Missouri Airbnb that appears to be a nice getaway option, but your love (or not) of squirrels may determine if it's the right destination for you.
If you're rich and/or famous in Missouri, where do you go when you want to stay in a treehouse? Believe it or not, there is an option and I have the pictures of this ritzy place near Branson to prove it.
Call me crazy but I find renovations of early 1900's homes into modern places to stay fascinating. Using creativity to keep the original era of the home while also modernizing it is no easy task. That's a pretty good description of Hannibal's Quarry House which was built in 1902, but has been renovated into a modern Airbnb option.
There's nothing quite like falling asleep when you have the Mississippi River nearby. If that's also on your list of "things you'd like to experience on a getaway", I found a place in Hamilton, Illinois that offers that and also an orchard view.