Very good point. I think paying for something useful let's say 5 USD one month when you use it is quite alright. But then go four months when you don't use it a

Very good point. I think paying for something useful let's say 5 USD one month when you use it is quite alright. But then go four months when you don't use it at all and pay 20 USD for that privilege is harder to motivate. But on the other hand, if the price was 1 USD / month it would not be such a big deal for those months, if it turns out you use it a few times per year.