Actually the cost of a Zinger is the same or more than an NX, Xoar, or other prop like that. Zingers are just easier to get at your LHS.
Here is a list of costs I found.

Pro Zinger 20x10 (Tower) - $23.99
Xoar 20x10 (Chief) - $22.00
NX 20x10 (Airwild) - $19.00

Just a couple examples. I have done some pull testing with Zinger as well. I do not rmrmber actuall numbers, but I do remember the Zinger turned lower numbers while also pulling less. It all comes down to what flies the plane best. RPM and thrust measurments do not allways translate into better flying. Seems like every plane/engine combo like a different prop.