it doesnt add up doing the math based entirely on aperture...
6" FPL53 blanks are a lot harder to come by than 5" ones Thus raising the initial cost of materials, figuring a larger objective as I understand it is considerably harder than a smaller one, and so raises the cost of labour. Demand for a 6" triplet APO is high, up goes that price again by a little...
Look at the Skywatcher Black Diamond scopes, or the Equinox series etc.. The 80mm is much less than half the 120mm in cost, however 80mm is more than half of 120...
You cant expect end product price to be solely based on aperture alone.. The tube would be more expensive to manufacture, would need to be stronger, the focuser would have to be re-designed etc etc etc....
I wonder how much you could buy a 2nd hand Meade 178ED for on Astromart... ??
