As with anything, the demand and supply rules of the market will answer this question. The best paid programming language jobs are the hardest ones and are generally the ones least in demand.
COBOL is a very old language used mainly in Mainframes which are huge, old and very powerful and reliable computers run by large organizations such as banks. Some Mainframes also run PL/I.
The other high-demand high-pay field in programming is Real Time. This means work with embedded electronic devices where time is of the essence. For instance, the software running on a laser guided bomb can't slow down or restart itself mid flight. It must be 100% bug free and 100% optimized. The languages used for this type of programming are C, Assembly Languages (varies by processor), and sometimes C++.
