They did, several times (breaking it down in to the $1 for production and $2 for processing/shipping like on that page). They also suggested $5 as a fair price,

They did, several times (breaking it down in to the $1 for production and $2 for processing/shipping like on that page). They also suggested $5 as a fair price, and pointed out that it cost them $3 to make the set one last time on a nag screen if you tried to pay $0 (fun fact: the site wouldn't let you donate anything greater than 0 but under fifty cents, since they would lose money on credit card fees).