If a route has lots of competition, it is probably not worth flying it. I find that (based in LHR) almost always, the smaller routes are more profitable than the bigger ones anyway. You would be better off buying 2-3 smaller planes (than A300) and 3-4 times as many small routes. You would make heaps more money.
The big problem with the A300, is that big routes have too much competition for them to be worth flying and small routes are too small to fly them without ruining the route and making less money than you would otherwise (I will note that I infact have 7 A300s, mainly operating on the aforementioned unprofitable routes from LHR and FRA, making less money than the smaller planes I have (about 200k each daily), so I am probably not exactly following my own advice...).