Bob:
You are also right, most optics buyers do not know or care about the
construction. They care about the optics and the value.
Jerry
Most people would not know or be able to determine that the FLs have glass fibre body housings instead of a magnesium alloy housing without being told that fact.
Bob
Gents
Trouble is folks who buy alphas aren't 'most buyers' and they, of all optics buyers, probably seek out details like this and the signs are that they didn't like the plastic. For myself, I thought GRP sounded like an engineered solution and liked the idea of it having some impact absorption rather than it transmitting impacts that overcome the armour all the way into the optics.
Seems the market didn't agree. Magnesium sounds better than plastic and one step more exotic than aluminium. Plastic sounds 'cheap' to some folks but I have read that obtaining machined fixings to the accuracy required for optical components is not a cheap task.
Lee