30 euro seems reasonable. In the US you can get unlimited everything for $30 a month (well, after some amount of data in the gigs I think it downgrades from 5G in the fine print).
There are a lot. Mint Mobile is $30/mo for unlimited if you pay for a year at once (a little more if you pay monthly). Visible is $30/mo but goes from 5G to 4G after 50GB (more expensive options have higher caps). There are lot of other ones out there, mostly trying to get people in the $20 range but with smaller limits on total data.
Now I remember why I switched from cricket. From time to time, I need data in Europe. On my US phone. That being said I should just switch when appropriate.
Thanks for reminding that.
I took the opportunity to check what the prices are in France now.
€20/month, and €10/month if you bundle it with your internet connection. ( bringing to a total of €40 )
I just checked the operator that historically has the better price. ( free.fr )