Summary: "We want to fill positions using ancient and obsolete systems that nobody would like to touch, BUT we are not going to pay any premium for it. We wonder why developers are not falling over themselves to come work for us."
When you ask HR to run an advertisment like this they don't have any idea what they are asking, they hear "computer consultant for this program" and look in their book of "What do we normally pay consultants?" Oh yes, here it is $30/hr, put that in there. So when you contact them and tell them $500/hr they will initially tell you "No thanks."
Then they will tell the person who asked them to write the ad that some "Kook" said they would do it but for $500/hr and the manager will say "Did you get their number? Are they local?" and the HR person will fall off their chair, then pick them selves up and sheepishly call you back :-)