Priorities determine how fast your render gets more nodes.
The higher the priority, the faster you get to the top of the queue.
The Cost Calculator is a rough estimation. Upload 2 or 3 testframes to verify rendertime and costs.
To make your payment as easy as you want, you can choose out of many payment methods: American Express, Apple Pay, Bancontact(BE), Carte Bleue(FR), Dankort(DK), EPS Überweisung(AT), iDeal(NL), Giropay(DE), Maestro, Mastercard, PayPal, SOFORT(EU), Visa.