In the short run, say a few weeks or months, there is likely...

In the short run, say a few weeks or months, there is likely to be only a finite number of people who know how to prune grape vines, for example. So even if the wage went up a bit, not many more people would be available and qualified. Given more time or some advanced information that substantially higher wages would be available, many more people would be available and the shortage would disappear at the higher wage. But, currently, there has not been time for the wage to rise sufficiently and no one knows if the market will remain tight long enough for the wages to adjust.