That's not the legacy price - basically if you look at the chart, from what it's saying is you can only purchase multi-month subscriptions if you have the standard package (40 char / 8 per server).
The chart is listing the monthly price instead of the complete price - the blue highlighted one is the best value for your money (hence the highlight).
For 180 day sub, you'll pay $12.99 / 7.99GBP / 10.99 EUR every 30 days for a total of 180 days (6 payments). the total cost will be - $77.94 / 47.94 GBP or 65.94 EUR
The multi-month subscriptions look a lot nicer when it's listed what you'll be charged for per month as opposed to the lump sums that I've listed above. It's a nice marketing tactic to make longer subscriptions look more appealing, even though you'll only be saving a little per month (Though it does add up!).
Around $2 / 1.30 GBP / 2.00 EUR per month, though if you add that up it can almost buy you an extra month of subscription.
$12 / 7.80 GBP / 12 EUR saved every 6 month cycle
I hope this clears up your confusion
As an edit:
The 'entry' subscription is best for those who do not want more than one character per server; it's at a permanent discounted rate because it suits those who do not and will not ever make an alternate character (but are still permitted to do so on other servers.).
The 'standard' subscription is well suited to those who would like to make multiple characters on the same account and are therefore charged a little extra.
Legacy is not being shown in the chart as we all know it's at an extremely discounted rate and that promotion is not being offered any longer so there's no point advertizing it for new players to wonder "Oh my gosh, how can I get Legacy?!" haha.
We are still unsure if Legacy will get multi-month subscription plans, but we are alredy getting a heavily discounted rate so I do not see it happening.
I hope I've answered all of your questions! Have a wonderful day!