While this is on point, generally, it's off topic from TFA.
Market forces are market forces, no arguing that and if you get left behind then so be it. What's insidious though, and what's discussed in TFA is how short-sighted many companies are. The big boss sees the cool new technology and opts to pay market rates that blow out the current internal rates to get it. What both he and his immediate underling (the PM here) failed to realize is that there's at least TWO key components to their new project (A) the hot new technology and (B) the deep-core knowledge of their current systems. (A) can be evaluated in the open market (B) can not be and if it wasn't for the senior programmer complaining, the company wouldn't have bothered to make an adjustment for him.
Now, programmers have choices... keep current with market skills and spend time doing this at the expense of not diving too deeply in the core guts of your current system OR maintain current skills and spend time learning the core system really well. Thing is, if you chose the latter your marketability is shot, you only know your original skills (but perhaps a bit better), but by the same token your value to the company (as long as that core system remains central to their success) also goes up. In a fair world you'd be paid based on your value to the company, cool-new-skills are generally valuable while deep knowledge of systems is only valuable to YOUR company, but still valuable. However, this rarely happens. Managers up the line tend to discount the latter and programmers specializing in the latter backed themselves into a poor position as the knowledge they learned doesn't translate into marketability in the wider market place and so WILL get a pay-hit if they leave (but the company would be hurt too).
And if you think the ideal programmer would do both, new skills and deep knowledge of current system, IMHO that's not feasible, if I had time to do both I'd still prefer to do more of the former as that is the more generally marketable skill and the one that's easier to convince management is the more valuable.
I think the company in question is a cut above average. They DID realize their mistake and took steps to correct it, but unfortunately they still made that mistake.