Seeing as it is far more efficient to make money through trading than through missions, most people will have that 20 mill to set up a fighter, anyway...how many times has anyone built up a character through missions alone?
(at, say, 5 minutes per mission (assuming we don't take the "kill 20 fighters, good work, but there are another 20 at the next waypoint" missions...), with an average turnover of probably about 30k (having accounted for explosive use...missions and lag are much harder to win without missiles), you're looking at 1,000 (that's one thousand) missions for a UAU mk 8...)
Anyways, as Jamez says...why do fighters cost 20 mill? Especially when they are able to take on so few other shipclasses...for only twice that, you can get hold of a gunboat which does all a VHF will do and more (for a start, it won't lose to another VHF, unless there is a huge skill gap...).