I would say that is still high for ultra. Imo:
Remove ads - $10 lifetime.
Ultra monthly - $1 per month, $10 per year, $30 lifetime.
I would definitely consider lifetime if that was the case. And you would have a ton more users signing up. The number of users should more then make up for the lower prices.
Edit: Question for people downvoting me, do you think I'm being cheap with these prices? $1/month doesn't sound much, but that is the point. It is still $12/year and the amount of users would more then make up for it.