In 2007 I completed and flew my -9 for the first time for a total cost of $64K.
The plane is a tip-up tail dragger and was unpainted, the interior was by Rust-Oleum, I had a Dynon D100 EFIS, D10 EMS (great combo, BTW!), DJM center throttle quadrant, Andair fuel valve, parking brake, fire extinguisher, five point Hooker harnesses, 496 for nav, iCom A200 Radio, Garmin transponder, Catto wood prop, etc. In short, a day/night VFR ship. (Empty weight at that time was 990 lbs.)
The big ticket item, the engine, was found on Barnstormers for $3500, had zero since major, etc. Here's the catch, that overhaul was done in 1959 and the engine was pickled. Also, it was an O-290-D2 and was set up for an adjustable pitch prop, not a CS prop.
I pulled the jugs and all was fine, see picture below, replaced all the rubber seals, converted it to FP, changed the accessory case to add a fuel pump & oil filter, and flew it for almost three hundred hours until I had a prop strike and replaced it with an ECi O-360 kit engine.
In short, you can build a really nice RV for less than $100K, you just need to be prepared to do more work than most of today's builders.

(Click to enlarge)
(See my website for details of my initial build.)
FYI - As the airplane currently sits in my hangar, it has a Dynon SkyView 10" w/ transponder, iCom A210, Dynon auto pilot, full leather interior, and that O-360 that is covered by a Sam James Holey Cowl. All those changes increased my EW to 1080.