If you are correct that other workers are willing to work that cheap, then the jobs would be filled.
Workers exist but are unwilling to work that cheap, so they're idle while employers have unfilled jobs.
Whenever you see a news story that says "employers having difficulties finding qualified workers," you can safely replace that phrase with "employers are unwilling to pay the market rate for labor."
[1] U.S. job openings hit record high of 7.14 million https://www.investing.com/news/economic-indicators/us-job-op...