expired Shoei GT-Air Motorbike Helmets (Limited Sizes) from $699.95 @ The Helmet Warehouse
They still have a few medium sizes left which tend to go first during sales. This was the cheapest deal I could manage to find without going overseas.
It's the best fitting helmet that I tried on but more expensive than my usual budget.
Covered by the ECE22.05 standards that were brought in this year. You'll find an E6 label sewn into the chin strap rather than an AS1698 sticker on the back of the helmet.