You don’t necessarily have to purchase full fare Y class to upgrade with 700 points.
An S class ticket will be a little cheaper and upgradeable too.
On the other hand if you’re hoping for a 100 points last minute upgrades 48 hours before the flight or even at the airport (providing you are a Silver/Gold/Platinum for the 48 hour upgrade and Gold/platinum for the airport upgrade) you will have better chances of an upgrade with Y class ticket.
ELAL’s upgrade policy has changed and they now look at the fare you have purchased rather then your statues, so if you are a Gold member with a Y class ticket you have a better chance of a last minute upgrade then Platinum with an S class ticket.
Policy is a bit strange, as it does not reflect the amount of revenue you bring them altogether as a frequent passenger but just on that flight…
You also need a minimum number of points in your account, and all these rules can be found of the website.