As per the official documentation RASA they say RASA is open source and free. If It is free of cost then why we see and Get a custom quote option under pricing tab? Is there there different flavours of RASA out which few are paid and other are free.? Can anyone answer this.
Welcome to the community 
Rasa is indeed free and open-source, but there is Rasa Enterprise which is paid.
From the website: “Enterprise subscriptions include the support, security, and collaboration tools necessary to run Rasa in high-traffic, mission critical enterprise deployments.”
More info here: https://rasa.com/product/pricing/