I've gone through this. If you want a year's subscriptions, you need to contact Jeppesen through the phone, and they have it available. There is a special price if you do the MX20/GX60 together, but I do know that seperately the GX60 costs $355 for a year. If you are looking for a one-time update, contact Garmin AT directly and tell them you need a one-time update for your GX60/MX20 combo, it should cost around $170 I believe, they mail you a new card, and you mail back your old ones. If you don't have the CURRENT SOFTWARE (not database) with you GX60 (Version 3.4 I believe) then there is a AD to update it to the new one and that should make it free for that update. When we contacted Garmin for an update in January, they sales person convinced us to wait a couple months, because they are working on a software update for the MX20 which should finish with FAA approval soon. So we will probably wait until our annual is due (end of March).
Contact for Garmin AT Sales is :
(800) 525 6726