Is it jus me, or do the marketing costs seem high fot this game? I'm spending about 40% of my income on it in this game
Welcome to one of the most common complaints about how the game works for "regional" airlines.
Marketing is a function of the number of routes you operate. Since routes in this era are so thin, most are forced to fly many thin routes to a lot of destinations. This increases Marketing costs. You're only experiencing the same thing that players who practice a similar model of flying many small aircraft to many small destinations experience even in later era games. I've ran the largest (in terms of pax) airline in the game, flying hundreds of F100s, while giving away over 40% of my revenues to Marketing costs -- and it's far from easy, lemme tell ya.
Eventually you actually get to a point where actually establishing a route actually increases your Marketing budget alone more than you make on revenue on the flight. You hit these points in the formula where your Marketing budget jumps up a large percentage when you establish a single new route. Makes for a not-so-pleasant surprise when you wake up the next morning to find that your Marketing budget's gone up by $25M/week because you added just one flight too many -- a flight that makes you only a tiny fraction of that.