You can find out two ways
Option 1: In the pricing page https://webautomation.io/pricing/ there is a calculator.
Enter the website you would like to scrape , it will then tell you how many credits you will spend per row
Option 2: On every product page the number of credit per row is displayed below the name
After each run you can see how many credits have been used and how many rows were extracted. With these numbers you can then estimate how much credit it will cost you for a larger run