HOW MUCH COST IN FIREBASE A CHAT APP?

Hi guys, I'm estimating the costs in firebase of a chat app. I'm checking the PRO template available in FF, and I can see this querys:

I have concers about the Chat query collection (in container). It calls all messages. This is the data base structure:

So, when users open the chat this will call all the messages? This not coud cost a lot in firebase? I don't know If one of you have a possible cost only for this, in case we have 1000 users chating with 50 messages per day for example.

Thanks a lot!