Just a few miscellaneous comments I wanted to add to the thread!
For the last few years I've hosted a program on some U.S based shortwave stations, I know there aren't many listeners these days but I do the show just because it's enjoyable to do. All caveats understood! Most of my work is done on YouTube and Online Podcast Platforms where a large audience is reached, but I still appreciate the more traditional broadcast mediums.
Aside from the already explained reasons for shortwave's decline, one other substantial issue that I have yet to see mentioned is the increase in RF interference. This is a problem that has been getting worse and worse in recent years, to the point where many listeners are even struggling to receive 100 kW stations with a portable radio when they're right in the target area. Sometimes there are ways to lessen the interference but many casual listeners are not going to hunt around to find out which appliance or device is causing interference and then unplug it, just to hear a radio show! The problem is especially bad for listeners in cities who live in high rise buildings, I've heard time and again from listeners who try to do everything right... they can't control what devices the guy next door uses though.
Low power shortwave stations (1 kW for example) may be more cost-friendly but the audience will only be the most dedicated of hobbyists and certainly won't be large enough for any sort of "revival". To put my money where my mouth is, I've used a number of the European low power stations before in an attempt to get a better signal to listeners in the U.K and Ireland. Due to the previously mentioned RF interference issues, not one single listener there was ever able to pick the broadcast up.
I've had the opportunity to broadcast on 300 kW and even 500 kW transmitters to Europe and North America, with that power the interference issues go away and even the cheapest of radios can receive the signal. The airtime costs are exorbitant though so the high-power broadcasts are usually just a one off occurrence here and there.
Despite that, shortwave is still a fun medium and I'm just thankful that I'm able to enjoy whatever's left.
I too have broadcasterd on shortwave, mostly WRMI.. for kicks and giggles. Good rates, good signals and audio. Broadcasted on a pirate SW outlet and one of the low power ones licensed in Europe.. i got a few listeners form there, but did it just cuse it was fun and chepa. I think more of my listeners, the few I had, came from WRMI. Jeff white is also very easy to deal with and a friendly guy.