Yeah, the game gets a lot easier as you go until it eventually looses challenge and gets too easy. At this point I have all the achievements, which unlocked a god mode. I got bored of it soon after.
Just keep doing practice runs to earn: collect money ups, try to hit speed gates, conserve all fuel (I turn off my engines quite a bit) and very importantly, land your ship without taking much damage. This gives you a big cash bonus.
Just fly with a little caution and patience and dont hit obstacles like a tard. If you do take damage, try and find some repair kits floatin around before landing. It's not always possible but long flys where you land back down gets you a **** ton of money.
Also when youre almost in space, hit all UFOs for extra money. The more you hit, eventually they start becoming worth more too. You also earn a special "defense" module that allows you to explode them for added bonus money.