Just had an email exchange with our Heroku (Salesforce) account admin - they claim that from August 1st, all Heroku accounts must be on a year or multi-year plans. No more monthly metered payments.
Update - after more prodding both representative mentioned that you can actually move to monthly. It's just something that they can't (don't) want to enable. "Heroku online" exists but being aggressively hidden.
