"You may attract more qualified people, but the number of unqualified people may increase as well."
...which is why you have a screening process.
When people are complaining that there are no good programmers (and this is a common complaint on HN; it's not just a straw man), there's at least one of two things going on:
Maybe the interviewing process is different where you are, but around here the salary is normally not mentioned in the posting - you'd normally get asked about your salary expectations once you've been through the interview.
I will not attend a long interview process if the salary is completely unknown. The least I do is to tell the possible employer what my expectations are and check whether this is ok for them.
Of course it would be better to make them define a salary range, but until now I was never able to do this.
It's a question of supply and demand. An hour or two for someone who is already working can be quite annoying when it's a dead end. On the other hand, it may lead to future opportunities.
Once you reach senior level development in popular technologies, companies are often eager to come after you. (At least, that's what the recruiters and help want ads seem to indicate about senior level J2EE developers around the Philly area.)
As the parent pointed out, in some areas/countries it's completely uncommon to announce salary ranges in job ads. What are you going to do then? Never apply? Move to another country?
I no longer apply to jobs where the salary is not advertised. After turning up to a few interviews in the past where the salary was well below market rate I don't bother wasting my time any more.
I'm trying to bring up an automated screening service at http://codeboff.in/ (self-promo alert) because I think we need way more of these, especially being the sort of people who could make them.
There is already codechef.com, codility.com, spoj.pl, online-judge.uva.es, ideone.com, turingscraft.com, etc. How is your service going to be different?...
...which is why you have a screening process.
When people are complaining that there are no good programmers (and this is a common complaint on HN; it's not just a straw man), there's at least one of two things going on:
1) Their screening process sucks.
2) They aren't attracting good programmers.
High salaries help with #2.