Quite a bit? Let's review:
Windows Xp (Home) - $100
Windows Xp (Pro) - $200
Office XP - $400
Norton Antivirus - $69.95
These are all much more expensive, and not only that--yearly costs. (Some even more often). mIRC, for $20, you get an unlimite dlicense to use this product and every release herafter. You can't tell me that $20 is unreasonable.
Additionaly, Khaled is sympathetic to the average user and offers a $10 purchase fee, or for the generous user $40. For a program you can presumably spend so many hours operating, and that many more easily customising, $20 is pocket change.