Hey, Railway only charges you for what you have used, more on how much each resource is being charged can be found in the pricing docs and at Railway's pricing page. What is important to note, is that the pro plan has a minimum charge of $20 a month (which also includes $20 of usage). You will only have to pay for the subscription (again $20 a month for the pro plan) if your usage is below the included usage (the pro plan has $20 of usage included). I highly recommend to give the pricing documentation a read, as it also includes examples for you to better understand how billing works on Railway.