Yes, OPTs have inherent insertion loss, and highpass filtering, and
limit achievable damping factors. It's my guess/opinion that that's
OK...a nice smooth rolloff over 20 kHz or so is okay with me. And I
think too much damping factor is probably not that great anyway even
though theory says it is. If you were driving voice coils directly
rather than through crossovers it would be more important.

If wideband low frequency magnetics were a mass market item the cost
would come way down, in the same way that a large car automatic
transmission is more complex than the reduction gearcase for a small
gas turbine, although the latter is many times the price. Indeed, the
whole engine would be cheap-if not as cheap as say a smallblock Chevy
and 700R4, certainly not twenty times the price-if manufactured in
quantity with competitive pressures forcing the profit down. Most of
the price of small aircraft gas turbines and the more expensive OPTs
sold to the hobby constructor market is pure profit. Volume is
relatively low, however.

I'm sure that the best 40-60 year old magnetics designs would be
rapidly superceded if there were a percieved need and market. As well,
superior vacuum tubes would be developed if a mass market existed.