You are mistaken.
OK, maybe not.
Back in the day, mid 80's, they were being sold, complete, for $600. Then the price steadily increased. OGT last, was selling stripped receivers for the $900 range. Then of course, one had to find some internals and a barrel. However, back in the day, those parts were, relatively, easier to come by than today. A complete parts kit with barrel was in the $500 range. So even at the worst, a complete one could be built for approx. $1400ish with new parts. Most every one of the imported ones were ex-IDF and purchased literally by the pound.
There has been some amazing things with the 40mm world. Some receivers were built from a block of aluminum, and done extremely well. Vary Vary nice.
What is a Colt 203 worth nowadays???? As per all the above reasons, hard to tell, and just what the market will bring. If someone wants one, could be lots, if there is no one who is getting a hard on for one, could be less than a couple thousand.
Most who have gotten them, haven't taken the time or effort to make or obtain proper ammo. Once the ammo situation is solved, they are a ton O fun. So we've seen some guys buy them for s&g but get rid of them later because they didn't use them. So some of these guys are getting greedy thinking the 203s are worth big bucks. But unless there is someone who is willing to pay the price, the money isn't there.
At least that's my .02c worth as a casual observer.