How much is being wasted? A lot of it. But media is not one of the big problems.

Media are formulated for various reasons. The first reason is to get something to grow in culture at all. This is hard. Most cells from mammals won't survive more than a few hours outside the body. Most bacteria won't grow in liquid culture. So the first thing a medium is formulated for is to get something to grow. Often you fail at this entirely. Leprosy is still cultured in armadillo footpads because we don't have a medium it will grow in. Penny Boston is probably the best in the world at this, and her artistry is basically thinking of what weird thing might put the right bits in medium to get some funny bug to grow. Rusty nails, for example. Getting a culture medium is a big deal.

Next is getting a repeatable culture medium. Old microbiology papers regularly used beef heart broth. That's made by boiling beef hearts and adding a few things to it. The amounts in it are completely uncontrolled. If you try the same experiment two weeks later with stringier beef hearts, and you get different results, is that the broth? Maybe. So we get defined media, media that are repeatable. Weirdly, that may still involve ground up critters. Luria-Bertani broth, which is ubiquitous, includes ground up yeast. We know how to culture yeast into a repeatable ingredient, though.

Then you have specialized broths. Can this organism produce its own ascorbic acid? Try to grow it in a medium without ascorbic acid. Once you get through a bunch of experiments like that, you end up with a minimal medium. Minimal media are incredibly useful for metabolism studies. Let me rephrase: they are essential for metabolism studies.

And then there are selective media, such as 7H9 used for mycobacteria. Tuberculosis grows in it okay. Very little else does. That's really helpful because almost every culturable organism grows faster than tuberculosis, so without a selective medium, you pretty much always get contaminated cultures.

And there are logistical issues. I know that if I grow my culture in a rich medium and then take cells from it and grow them in a minimal medium, I will get different results than if they were passaged through a minimal medium. That's not genetic, it's just physiological adaptation. But in tuberculosis, rich medium takes weeks to grow a culture in. Minimal medium takes months. Better to do a bunch of experiments in the rich medium to minimal medium, see if I find anything, then check if it's an artifact being held over from the rich medium. Cell culture studies aren't as long, but the same argument applies.

Plus every time I start working in a new medium, I have weeks or months of experiments to calibrate it, make sure I know how it affects what I'm studying, and get the data to be able to compare it to my previous media. It's a big investment, so most labs will have a handful that they use.

Meanwhile the organisms are also evolving under the selection pressures you're applying by growing them in these crazy environments. Formulating lab experiments that remain relevant to the world beyond is a difficult, detail driven subject and can go horribly wrong in many fascinating, mind bending ways. So there's a lot of wasted money in research, but it's not because of this stuff. This is table stakes, because biology is hard.