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On the subject on the ultimate `value' of the mass produced optics :
It costs money to anneal optical grade glass to be strain free as it takes a lot of energy to keep kilns running at high temperatures over many days . This is a particular area where the budget mass produced dobs companies save money.
Those optics are not made with a view to holding a precision figure over a long time , just as the particle board mountings are not meant to last 20 years - they are simply made to a price. A well known US optician won't refigure one of these mirrors until he has re-annealled the glass.
It is not possible to look at the strain / anneal of these blanks when they have coatings on but I have had the chance look at some with coatings off and have never seen one that you could call fine annealed and some are positively horrible yet have given the owners a reasonable view so far . Optics are no different from any other area - there are generally no free lunches.
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