a. Debuggers
b. IDEs
c. Querying Tools
d. Text editors
e. Source control tools
f. Build systems
The market for development tools does not look particularly vibrant based on the above.
The huge problem with them is that they're proprietary. They don't have the wide usage of the open source equivalents, so debugging problems is hard. If you want to develop at home, at work and on a PC in a lab, you have to navigate licensing issues. If you want to do a build and test as part of your CI process, you have to navigate licensing issues. Then you move jobs and they've bought into a different, incompatible proprietary system and you have to learn it all over again.
The open source options are actually good enough, and the advantage of being able to have the entire build system on a new computer after running a few apt-gets and downloading some free software is huge. The skills persist across jobs, I can use them at home for my own projects, I never have to worry about licenses expiring.
But, these are all pretty easy to start for a single hacker who can recruit help to expand an open source version.
Don't we spend on software, though? Software spend is surely in the billions, if not tens or hundreds of billions a year. As consummate consumers of software, I'd think software engineers are more likely to spend money on software than the general public (and more likely to use open-source software as well).