I have had good success using miles or upgrade coupons. I see that you are Gold Medallion. If you can make it to Platinum, Delta will give you a choice of gifts. One of which is four upgrade coupons. These can be used for upgrades to Business Elite from an M (or higher) class coach ticket. The M class tickets are not $1,600, more than likely around $2,800-3,000. With the coupon (or 25,000 miles) you then upgrade to business class. Much better than $11,000. You need to call them to book a ticket this way.
If you do not have one (and travel with Delta a fair amount), go get a Delta Amex card. They give you good mile benefits and if you get the right level card, free access to DL lounges even if you fly coach.
I am a believer in picking an airline and only flying them (I also happen to use Delta). The other week, I was upgraded for free on the way back from DUS to ATL. First time that has happened!