You get a discount as well if you pay with crypto 
Yes, they offer the payment in Bitcoin, Bitcoin Cash or in Monero and you 10% discounts on them but if you use Bitcoin, then the refunds are not supported.
I chosed NordVPN because it had a very interesting discount, I think it was 70%, so I took advantage of the 2-year package promotion.
How much does it cost you per month for a 70% off for 2 year package? I have seen Express VPN cost you around 6.67$ a month if you buy their yearly plan and Mullvad VPN is still cheaper even if you buy it for a month. However i heard that Mullvad VPN support is not as good as other giants in the market like Express VPN etc.