I’m wondering what the price tag on these would be :)

This item is odd in that anyone who can earn this weapon, can and probably will use it as well. Whereas anyone who cannot earn it, cannot use it. I'm only speaking in terms of its use as a battle weapon though.

But keeping the above in mind, I don't feel like you could feasibly find one for sale below 500mil at the least, and yet for myself, I would probably not even pay 200mil for it. Not the most helpful pricing advice, but my two cents.

is on the right track. It's too useful of a weapon for a serious battler to give up unless they have quit battling or quit subeta. It is the best obtainable "god" weapon out there for the most part. You probably won't find anyone willing to part with theirs for anything less than an insane amount (3bil+) because you can only get the achievement once.