I just realized there are two versions of antbuster.

I had been playing this one http://www.thegamehomepage.com/play/ant-buster/.

It doesn't allow you to get sniper 3, missile 3 etc and cannons are more expensive, i.e. much harder.

http://www.rstein.org/antbuster/

Thsi one is much easier. I was wondering how everyone was doing so much better than me.