The quality of your audio has an impact both on the intelligibility of what you're saying and on listener's subconscious evaluations of you. Audio software and hardware is also cheaper and much, much easier to deal with than video--I've had no problems with essentially the same setup across Mac, Linux, and Windows.
The cost of entry is somewhere around $50-$100 for USB microphones, although if you're willing to spend closer to $250, you can get a decent USB audio interface ($120) + standard (XLR) microphone ($100) + XLR cable ($10) + stand or boom arm ($20).
I've been in countless online meetings where I'm barely able to hear one or two of the participants.
Every time I've evaluated a better video setup, it's been clear that there are a bunch of things you want to get right in order to have a smooth & reliable experience. You want a camera with clean HDMI output, a capture card, and make sure that your camera can be run continuously for as long as the meetings will last--don't forget back-to-back meetings. If you might be in meetings for three hours in a row every once in a while, do you need a camera that can be run for three hours continuously? Most "proper" cameras just can't do that. If you dig into the specs, some of them will list the maximum amount of time that they'll run before shutting off. Twitch streamers and people who run YouTube channels have done the research and will tell you which cameras are suitable for this kind of work, but at that point, you're often spending like $700 or more just so people can see a clearer picture. I would love it if I could just use my DSLR, which is a very nice prosumer DSLR with some nice lenses, but it's just not designed for streaming video. I would have to buy something new.
High-quality audio for $50-$100 is a much, much better deal.