Bind the Sealed Sword upgrades to the owner immediately.
Obviously these weapons aren't intended to be owned by players who haven't taken the time to rustle up 25 jelly gems, as indicated by the bound nature of the Sealed Sword. I like that one of the most powerful weapons in the game requires a little effort.
However, once you upgrade it, like all weapons it is fully trade-able. Can this be remedied?
Alternatively, if making this weapon more difficult to obtain was NOT the intention of the development team, perhaps unbinding the SS on pickup is in order.
Also, all points apply to the Antigua chain as well.

I agree that there should be measures put in place to disallow players from buying their way through the game/ forcing a little effort

I actually like this idea as well, makes it less obtainable, and when I finally do get this weapon I will feel much more accomplished.
definately for this... i'd like it if there was some kind of effort players had to put in to get a specific item. especially sealed swords and antiguas. i really don't want this game to end up being: 'anyone who has money can get to tier3 in under an hour' just because there are sellers out there.