If you go after one (or a few) person in particular, it's ok to ask that question. In fact, if you go after one person in particular that you know is a great fitting, there is almost no power disparity and lots of things become ok.

But if you decide to just poll undifferentiated candidates to extract valuable information, well, that's really not ok.

Are you telling me startups don't have budgets predetermined before the role is ever even posted?

Yes, for roles we’ve never hired for.

In which case to find the market salary, we ask candidates (candidates are the market, we want to pay market rates. So, we ask candidates)

This isn’t just startups.

Some companies have “bands” that define the range of pay for given titles, but many don’t. Even those that do are constantly questioning whether they are the right ones based on a wide variety of factors: Are salaries moving up, or moving down? Are there few candidates, or many? Is the value of this role to the company increasing or decreasing? Does the company have the cash flow? Will it have the cash flow in six months or a year? Etc.

Sitting on either side of the hiring relationship it’s easy to simplify and vilify the other side. But it’s foolish to do so. Over time in your career folks may be on each, in turn.

I dunno, a two minute LinkedIn search or Glassdoor search will give you all kinds of metrics for all kinds of roles and for companies at different stages, so I don't at all buy this argument.

Especially for developers, you can get a crazy range of quality, experience and location at different multiples of cost. Like if I was buying a car I first determine my needs and money to spend then start searching in that band of prices. What if I just went to a cqr salesman and asked how much are you expecting to make from this sale? Is that a smart starting point for anyone?

If I ask my favorite search engine for "technology salary guide", there are several first-page results that at least claim to provide just this.

Are these less reliable that they look like they think they are, or... ?

> There’s no bible saying what “market rate” is for every given role

there actually is. there are multiple salary benchmarks available. you should be using one.

Market salary information is out there and it shouldn't be too hard to figure out where you, as a company, want to place yourself. If you're going into interviews literally not knowing what the market rate is, you're wasting everyone's time.

Yes, it's a candidate's responsibility to know their worth and communicate it to prospective employers. If prospective employers are ignorant of the market, they just look like they're unprofessional.