I don't know of many geeks/private individuals who own a 1-letter domain, so I would consider it a loss to give up y.nu. But 500 EUR just for the fun of having a short e-mail address is a luxury I won't be able to afford forever.
My idea: if there are a few nerds around interested in doing something nice with this domain (short URLs for service you want short, like URL shortening or the my-IP service on ip.y.nu - and of course short email-adresses) let's share the cost...
So: if you would like to have a short email (like a@y.nu) including a matching A-record like a.y.nu (or a full delegation) and are willing to share the yearly cost, mail me at r@y.nu (try to mention save.y.nu in the subject) as long as this is still possible :) Expecting about 20 participants about 20 EUR/year for a 1-letter Subdomain should be fair. Offer whatever you want for longer names you'd like - there are surel.y man.y sill.y options to build. I prefer bitcoin payment and multiple years in advance ensure your ownership of the delegation for that time...
In the hope to get this to work...