It recently occurred to me....

DL offers a rountrip Concorde award for 160,000 miles. Those whp participate in AMEX Membership rewards can buy 20,000 miles for $500 each month. Spend $4000, get 160,000 miles transferred to DL, and you've got yourself a Concorde ticket.

Yes, it's expensive. But it's a lot less that spending $10,000 rountrip!