I've been focusing on building RF gear for the last year or so, mostly stuff comprised of individual transistors and the occasional op amp.  This is its own kind of rabbit hole because many of the components from these 80s era designs haven't been manufactured for fifteen to twenty years. 

I have an active "hunting" list of forty or fifty parts, mostly BJTs, FETs, and small scale ICs that are used over and over again in the designs I am trying to replicate. Because I was a bench engineer in the 80s, I know they were once cheap and plentiful.  Today, assuming you can find them at all, the going prices are often astonishing.  

The old HP2800 pin diode, which probably cost less than a dime when it was being produced, is now hard to find for less than ten bucks. When you need four of them for a mixer, well, that gets to be a pretty expensive project pretty quick.  And the dual gate MOSFETs that Doug Demaw used everywhere in his QRP rig designs? At the going rate of five to thirty-five bucks a pop, a receiver with six or eight of them is costs way more than an RTL-SDR dongle.

That said, I like building with unobtainium.  Tracking down rare parts and, better yet, finding a stash of them that I can afford, is as much a part of building as waving a soldering iron around.   Maybe I am weird, but when I manage to score a dozen Johnson air variable caps for two bucks a piece or someone offers me a handful of RF transistors that I've been hunting for a year, I am having a pretty good day. 

Is looking for this stuff as much fun as building? Nope... but some days it is pretty close.