Bio is dire for two reasons, IMO:

1. NIH stipend levels are pretty low. When you talk to people on NSF or DoD funding, they're like "You pay your postdocs what!?"

2. There are fewer "eject" options. Physics, for example, has a long and established pipeline into finance. The group I'm with does lots of work on complex networks - that has applications in tech. Bio work, for the most part, leaves you qualified to do bio work. So there's both less salary pressure for "We have to pay you or you'll go work for tech instead" and the feeling of your education being a sunk cost.

Don't worry about the stipend levels. Many institutions are now in a race to the bottom where they're adapting to paying everyone the minimum allowed by NIH.

Even in Bio it is not that bad. It took my brother an extra year than he wanted to find a post-doc(cell biology), but he is making over 40k in an affordable midwestern city. It's good enough that he can rent a 2 bedroom townhome by himself in a nice part of town.

It's good to know. The ones I've looked at (physics-y) were about $32k, but maybe they were especially bad. This was at a public institution (one of the UCs), if that makes any difference.