It's odd but my local Subway restaurants have had $6 footlongs for quite sometime. Their recent commercial touts the $6 price for February, hoping we'll forget their entire $5 Footlong alliterative jingle and that their sandwiches used to be cheaper. 
I didn't see it on their web page menu, but if you can get their Pastrami Melt (ask if it's part of the $6 campaign), it's a huge bargain at $6. It's regularly their most expensive sandwich (over $9+ for the footlong). Add the cheese of your choice and get it toasted. I add avocado (I used to add their spicy guacamole but they stopped carrying it), some onions and mustard.
Them's good eats. 
They also have started a "deluxe" feature. It's not double meat but a half serving of more meat for 50 cents per 6-inch sandwich. So a regular ("classic") tuna sandwich would be two scoops of tuna salad per 6-inch sandwich. Four scoops per 6-inch sandwich would be double meat and "deluxe" would be 3 scoops per 6-inch sandwich.
edited to clarify
