We said $30 because that's what we used to pay
The posting said $30 an hour. In the interview the number changed to $15, and the interviewer explained why: that used to be the rate, but the economy means they can get good applicants anyway.
If he did not take it, someone else would. He could work up to the advertised rate in about five years, if things improved.
Most bait-and-switch is deniable. This employer priced the posting at what the
job was worth, said in the room that it intended to pay half, and gave the
labour market as the reason. “Someone else will take it” was not a threat
thrown out in frustration — it was the whole negotiating position, stated
plainly. The five years to reach the advertised rate depend on economic
conditions the employer neither controls nor has any obligation to honour.