From a non-airline pilot trying to get a grasp of this...
J* Offer DEC to foreign pilots because they don't have the numbers to fill the seats, fair call as this doesn't take away from FOs moving up. However there are Aussie pilots flying overseas current as Capt. on type who would come home if the price was right. Airlines don’t want to pay the price and therefore declare shortage of pilots. Using this declaration the airlines then get permission to bring in foreign pilots to do the job.....
Could I use this same logic and say.... offer a job paying $10hr to work at KFC, no one wants to work for $10 so I say I have a worker shortage, the gov then gives me 457V and I get a bunch of foreign workers over to do the job. Because this cheap workforce is now available I can pay the rest of my staff $10 as if they don't like it I can replace them with more foreign workers... Am I close???