Do you have to pay every month for Bubble?

Could you please clarify for me, is it necessary to make a monthly payment for Bubble? I'm trying to understand the cost structure and want to ensure that I'm not missing any ongoing expenses. Could you elaborate on whether this is a one-time purchase or a subscription-based service? It would also be helpful if you could explain any additional costs or fees that might be associated with using Bubble. Thank you for your assistance in clarifying this matter.