... Especially at a fiver or more each treatment. Apiguard or a straight thymol treatment might be a far better option monetary-wise.
Not sure I follow your logic on this occasion.
Raw Thymol is obviously going to be cheaper, but financially should be compared against straight Formic. They are both cheap. No argument on that score.
But the products are providing a safer, more pleasant, controlled and convenient means of applying the active ingredient
Taking T's pricing (without shipping) for a simple comparison
Apiguard £5.26/treatment (based on buying a pack of 10 trays/5 treatments)
MAQS £5.52/treatment (based on buying a pack of 10 treatments)
I honestly don't think that 26 pence per colony treatment represents "a far better option monetary-wise".
What that 26p can buy you is an extra month of production.
Which I think has a greater value than 26p ...
My conclusion, so far, is that MAQS would be better used a bit earlier. There is no need to delay it as late as possible - as with Apiguard.
I haven't seen much in the way of bee losses.
When we get a bad year of mite infestation, using it early, with the supers giving extra volume, should be considered pretty normal.