Costs shouldn't rise or fall based on the price of the coin. You can pay directly in USD for the storage so that you don't have to worry about the pricing shifts.
Sure, you pay in USD, but the network accepts payments in sia/storj coins. What happens if the price of the coin goes to the moon? Is the service provider (storj.io) going to eat the cost?
CTO here! There's no cost to eat. We determine the amount of STORJ to transfer given a storage node operator's USD-valued accruals at the time of transfer. All of the book keeping is USD-denominated.
>We determine the amount of STORJ to transfer given a storage node operator's USD-valued accruals at the time of transfer.
So you have agreements with storage node operators to provide storage space to you at fixed costs (denominated in USD)? Or are you paying whatever the market rate is for storage, and hoping that it won't go above $4/TB?