I've just bought a couple of new MacBookPros and the dual-link dvi cables are on backorder for 4 - 5 weeks. I will be getting the 3090 as soon as this cable is available. They said it will be available around Xmas.
A plug for my favorite online store, Provantage
. Their price on the 3090 is $1899.99, and they have over 100 in stock. Delivery was $25 and I got it 3 business days later, with no sales tax.
I have been ordering from them for years. I get my roll paper and HP Z3100 inks from them, and they generally have the lowest, or close to the lowest, prices on the web, depending on the item. They have proved themselves extremely reliable, in my experience.