Disclaimer: I work at Backblaze.

> currency conversion is expensive

Backblaze probably won't accept other currencies in 2018. However, we definitely have heard about this issue, and we have a feature in the works to allow you to "load up" your account with an arbitrary amount of pre-paid cash so that you pay ONE transaction fee to deposit (as an example) £250 pounds at once (incurring the £2.50 conversion fee exactly once) and then as Backblaze deducts from this account balance instead of a credit card there are zero transaction fees.

Would that help?

The OTHER reason this is a requested feature is some customers want a "reserve fund" to be used if their Credit Card payment fails, as a hedge against Backblaze deleting their data for lack of payment.