The problem is that in cases like these, invariably the old, crappy code contains documentation and functionality that will never be reproduced by a ground-up re-write. Understanding the old code and rewriting is, in general, just as expensive as refactoring. This is the common dilemma with old codebases like this -- in spite of its horrible, unreadable state, it contains business knowledge too valuable to lose.

As far as making the code "look nice" -- you've missed the point. The goal is to make it functional, readable and extensible again, and doing that to a 1M+ line codebase (which I've had to do) can be enormously rewarding, the business value gained more than tangible.