Well, cost is not at all linear, compared to size. No matter what you fly, you need quality servos and radio gear, so that expense is virtually unchanged from the 40 size to a 110 size. If you want to build, a CA Models Epsilon 60 flies well on a ST90. There are a number of 110/120 sized ARF's that fly well and are not overly expensive. If you are not concerned with staying current in pattern ships, the Kaos/Chaos series by Joe Bridi are excellent aerobatics trainers and kits are very reasonably priced from Bluejay Airplanes. No ARF's, though, so you have to build to get one...

http://www.bridiairplanes.com/

Keep in mind that pattern planes are more precise than regular sport planes and are sold to a small niche market, and they cost accordingly. A more expensive aircraft does not necessarily fly better. Much of the benefit/performance of a pattern plane comes from careful building/assembly and trimming. This can be applied to any aircraft you buy and the benefits are always available to those willing to take the time.


Mark