"Get a whole year for 129 USD that's less than $3/month!"
However, the "Extend" button says:
"You will be charged $29.00 USD for 1 year Premium upgrade."
I've also found a related issue: the expiration date in the todoist.com/premium page and the settings page aren't the same for me.
Somehow the settings page shows me a 2015 date, when the premium expiration for my account should be in 2014 (unless the Todoist team is actually giving me/us a free year :P).
For me it's a month difference.
Thank you for your reports. The pricing issue is now fixed and says $29.
Reg. the Premium time issue - we're looking into it now.