The manufacturers of certificated aircraft pay LyCon prices because the
only alternative until very recently was an Allison or P&W turboprop at
ten times the cost. I'm not sure any of the other supposedly
certificated engines being talked of are 1) actually certificated in
the U.S, and 2) actually shipping. The Zoche and DynaCam were thinly
veiled efforts to pimp up some venture capital; neither had any real
desire to produce engines.

Homebuilders use these same engines because most homebuilders today
just want to fly and are "building" as a dodge around type
certification: most lack fabrication skills or any desire to
experiment. Look at Richard Van Grunsven, who is making a lot of money
on the RV kits. If people will pay those prices for sheet aluminum
and assorted widgets why should he get his airplane certificated and
tool up and manufacture them? His margins are as high as a certificated
lightplane, he is making a lot of money with relatively little work.

If the Lycoming or Continental engine were really more reliable than
commodity general purpose engines, they'd be used in many other
applications. They are 1930s designs that if not protected by
certification would have been out of production for decades. General
purpose production engines have been installed in aircraft, usually by
people with a lack of resources in manufacturing and design, and yet
flown pretty well. If a company like Mercury Marine chose to get
involved in powerplants for experimental aircraft, they could put
Lycoming out of that market segment in a couple of years.