Is Bubble Cash free?

Could you please elaborate on the topic of "Is Bubble Cash free?" I'm interested in understanding if there are any costs associated with using Bubble Cash, or if it's entirely gratis to its users. Are there any hidden fees or charges that I should be aware of? Additionally, does Bubble Cash offer any premium features or services that require a paid subscription? Finally, could you provide some insight into the sustainability of Bubble Cash's business model, given that it's purportedly free to use? Thank you for your time and assistance in clarifying this matter.