Today I got this reply from MAC customer service:
"Thank you for taking the time to contact MAC cosmetics online.
Please accept my sincere apologies, There has been an error with the retail price for the eye shadows within the Cool Heat Collection. It was a keying error and the brand are doing as much as they can to rectify this matter with all of our retail stores.
Please return to the MAC store in Nottingham where you purchased the Shadows to receive your refund.
Once again, Please accept my sincere apologies for any inconvenience caused.
Kind Regards,
Monique Stobart
M.A.C Cosmetics Online Customer Services
0870 0342999"
Luckily I kept the receipt, I'll let you know how I get on! Hope it's not a problem.... :-S