That's just business though. If they came out and said "We can offer up to X amount" then everyone would ask for the highest amount, they wouldn't say "oh no, that's too much, I'll take the lower end of the bracket." It's just like negotiating the price on a car. It's their own responsibility to research what their job (or car) is worth, and it's not like it's hard these days with salary calculators and things online.
Not being able to be picky about your job/salary isn't discrimination, it just is what it is. It would be discrimination if a company was systematically hiring women and men with similar credentials, and refusing to pay women as much as the men. Who knows, that probably does happen at one or two companies because people are scumbags, but it would be interesting to try and prove.