Got offered DCC at an ATM in Thailand at the airport in Bangkok in December, using Kasikornbank (K-ATM).

Rate that day THB 33.00 = 1 USD.

Withdrew THB 9,000 and charged THB 180 service charge by ATM (I used to think the 150 baht charge was a ripoff!)

My Capital One debit card was charged USD 278.21 (only 2 cents off from the exact rate.)

The DCC offer was USD 292.99 (including service charge), a 5.3% markup.

Thanks, Kasikornbank, but I'll save my $14.78!