It irks me big time when online services lie to me about pricing.
If your plan costs $12/month, charge me $12 for one month. If your plan costs $30/month, say it upfront.
If you say your plan costs $12/month but that $12/month applies only to annual subscription - and you actually charge $30 if I want to subscribe for just 1 month - it means your marketing department just lied to me. And that is not a nice way of starting a business relationship.
Most US-based startups pull this nonsense.