And the really frustrating thing is - there are people (like me and others on here right now) who'd be perfectly happy to sit and unravel and fix this monstrosity, but software development "how long is that going to take? And you'd better say a day" methodology prohibits any sort of complex/deep work.
Why would they choose you, when the contracted company can bill $300/hr per developer for 'change requests' to fix the system. They don't want to fix it, they want to fix each individual problem as it comes up.