In the context of codecs we're actually seeing how it prohibits improvements of technology.

Broadly speaking (i.e. I'm sure there are counter-examples, but they are not significant in the big picture), people didn't patent compiler technology, and we had great progress in compiler technology.

People didn't patent database technology and we had great progress in database technologies, from both academic research and competition.

People didn't patent word processing technologies so that Google can re-implement Word functionality in the browser because none of the fundamental techniques have been patented. Again, lots of progress from competition.

For whatever reason, audio and video codecs are heavily patented and the technology is ludicrously outdated compared to what it could have been if we had progress from competition or academic work of free software implementations because the patents cover basic ideas in compression so no-one can build on them and patent holders have no incentive to improve the technology because it's much easier (and more profitable) to just collect royalty checks.

However, developing video codecs isn't any more expensive than developing databases or compilers or word processors.

See e.g. h264 encoder which is an open-source effort by few amateurs that is widely regarded as being of better quality than commercial offering costing thousands of dollars (because of patent monopolies, not because they were so expensive to develop).