Glow fuel is not cheap, but if you consider all the costs for the alternatives, then it's not so bad.
With a .60 size trainer, you could get a .90 four stroke, Hobby People sells a Magnum .91 for $ 159.
They have a great sound and use a lot less fuel then an equivalent 2 stroke engine.
If you want gasoline, check this out : http://www.maxfordusa.com/mentor-g26cctrainer.aspx

A bigger plane has a better handling, you can see it better and it can take some wind better then a smaller one.