OTOH, all reasons are cons... an expert in an esoteric system with none of those will be paid her weight in gold by the fewer employers in need of a very finite resource... while js programmers are a dime a dozen.
If one language is expensive, and another language is cheap which do you think employers will be building NEW software in?
I've seen people who follow the strategy you prescribe, and while they did make above market while they helped companies migrate away from [dying technology] they eventually became unemployable.
It simply isn't a good long term play, for either employee or employer.
In the long run we are all dead. -- John Maynard Keynes
For some, the short term payoff is the right strategy. Also how is it not good for the employer? Assuming they could fire the person (or just hire him/her as contract).
Weirdly enough, this isn't necessarily true. Articles keep popping up about a shortage of FORTRAN or COBOL programmers. Yet when you look into it, they pay comparatively poorly... which explains the "shortage". I think this might be because there's still enough retired folks willing to contract a bit on the side. (And FORTRAN is not so bad.)
On the other hand, you can definitely demand obscene hourly rates for old, clunky stuff most people don't want to touch. Sharepoint is one example I know of. (Not to imply CF is clunky, but the worse the workflow, the higher the rate, obviously.)
> Yet when you look into it, they pay comparatively poorly
Hmm. I know this is completely anecdotal, but the two software engineers I know who are COBOL experts also happen to be the best-paid software engineers I know, and not by a little.
Old, esoteric systems also require knowledge of the system, which can be practically impossible to get from the outside. This is why learning COBOL in 2019 probably won't get you a six-figure job maintaining old bank mainframes. You may know the language but if you have no clue how these bank mainframes work outside of using COBOL, you aren't going to be a great
candidate.
I've seen people who follow the strategy you prescribe, and while they did make above market while they helped companies migrate away from [dying technology] they eventually became unemployable.
It simply isn't a good long term play, for either employee or employer.