So you’ll be able to buy Arks Cash through ISAO. What does that mean to you? Well primarily what it means is that as a foreigner you’ll be able to buy Arks Cash at all, as ISAO accepts foreign credit cards. So if you were eager to burn a hole in your wallet by playing the gachas, or wished to just pick up the odd shortcut item from time to time, you may be able to. This is not complete confirmation, but I don’t think they’ll deviate from the system they had with Phantasy Star Universe somehow.
ISAO is able to accept Master Card, Visa, JCB and American Express cards. A list of other payment methods can be found here (Japanese), although not all will necessarily be available for PSO2.
Players of the Japanese Phantasy Star Universe servers from years back may know better, but before the switchover to ISAO players had to pay for their subs using NetCash cards that they’d have to buy from 3rd parties if I recall correctly.
The actual worth of Arks Cash still hasn’t been announced, nor has a list of prices for each item been revealed, but there was strong speculation among Japanese posts on Twitter that it would work out to 1 Yen per AC. This has neither been confirmed or denied, however the cash shop currency for the previous game in the series, namely Guardians Cash, worked out roughly to that.