To add to your sample set, I'm a rails developer and also get paid handsomely. My salary is higher than it would be for a C# or Java dev of the same experience. There's a shortage of rails developers in my area I think, but plenty of C# and Java devs.
It seems like different languages top out at different amounts. For instance, a junior PHP developer may make the same as a junior .Net/Java/NodeJS developer, but the PHP developer is going to plateau long before the Java developer.
But they are all going to plateau if they don't get some architecture/team lead/full stack skills.
I think I have maybe a good three years before I plateau as an individual contributor. At a certain point, no one is going to want to pay me more without forcing me to lead a team (been there done that didn't like it) or becoming a consultant.
I'm not saying it's impossible to make at the top of your market with Ruby, but the odds are stacked against you.
I think that Ruby has lost its “cool“ factor whereas .NET is back on the rise due to the release of .NET Core and TypeScript, so a lot of people have moved away from Ruby which leaves those of us who still have an interest in it to fill in the gaps.
It also seems like every year we hear that “Rails is dying”, but I don’t think I’ve seen those claims materialize. It’s maybe not as popular as it was 5 years ago, but I’m not hearing any death knells.
Not saying anything about Ruby in particular but you never want to skate away from the puck unless you’re near retirement and want to make some quick bucks - like people still writing COBOL.
There is a balance between number of available jobs and the pay. Go is the top paying job but you may find yourself being unemployed for awhile or stuck at a job you don't want looking for Go jobs.
Ruby may pay more but once you get to the higher end of the scale, you'll find many fewer jobs paying the amount you want.
EDIT:
In 2008, after being at one company way too long, I was what would be considered a top C developer and there was a company offering me $20K more than I was a making. But I saw the pickings were slim. There were more jobs paying the same amount for “Enterprise C# developers”. But I wasn’t qualified for them. I took a job paying only $7K more than I was making as a high entry level C# developer.
10 years later, there are no jobs in my local market paying $65K more than I was making in 2008 for C or C++ developers. There are some paying C# developers that amount (I have one).
I’m not bragging. According to all of the data I can gather, I’m making the median for my market for a “.Net Architect”.
That seems totally reasonable (and I don’t see your sharing some experience as bragging).
I guess my point is that high salaries aren’t limited to .NET and Java jobs. I guess I’d also challenge the idea that a Ruby job paying $100k+ doesn’t “pay well” (outside of SV anyway). Fast food doesn’t pay well. Working in the higher levels of tech absolutely does. My very first job was working the drive thru at a Taco Bell, and it still blows my mind when I think about how much I make now... (also not bragging, just trying to add some perspective).
It’s not just about pay. For instance, I could go into management. There are a lot of reason I don’t want to. But one reason is that managers seem to get “stuck”. It’s not as easy to leave because there aren’t as many jobs for managers and if you are forced to leave, it takes longer to get a job. I can have another C#/Java/NodeJS job within two weeks (if I was qualified).
Source? I know I’m an N of 1, but I just got hired to work on a Rails app and the pay and other benefits are pretty competitive...