For anyone who wants to use Crysta, 1 Crysta = 1¢, so a subscription that costs $14.99 would cost 1499 Crysta, and so on with the other subscription options.

You can buy Crysta with a credit card at the MogStation, or (at least in the US, not sure of elsewhere) you can buy Ultimate Game Cards at retailers and use them to buy Crysta. (The two step process of Ultimate Game Card -> Crysta, then Crysta -> subscription is the way for people in the US to get game time without a credit card, since FFXIV game cards aren't available in the US.)

Oh, and for the multi-month subscription options, SE's site (at least the one I found when I was settting up my sub) only displays what the equivalent per-month cost would be, but you have to pay the entire amount at once, so for instance when they say a 180 day subscription is $12.99 per month, they really mean that it costs $77.94 once every six months.