I cringed at the price but I bought the Bose A20 this summer and wish I did it years earlier. I mostly fly 767 freighters and they are loud. Flights can be as short as 30 minutes to 10 hour plus.
I'm a retired Army Reserve Aviator, flew mostly helicopters. Hearing conservation was emphasized from day one of training. I faithfully wore earplugs for my entire career.
On the civian side, I flew CRJs for 7.5 years and wore a Telex with earplugs off and on. Then I got into Boeings in 2007 and have flown 747,757,767 where the bulk of the pilots would rather yell over the ambient noise rather use the intercom. All that effort to keep hearing loss at bay I think was squandered because of my laziness flying these planes.
Now that I'm Captain, I insist that the intercom is used. I love my Bose A20. When I take a break I don a Sony NR headset.