if people think a 113 activity is valuable then i wonder what people are willing to pay for mine
A well known Legendary account, with over 7000 posts, on the DefaultTrust list? A lot, I'm sure - and, after that post, I wouldn't be surprised if you had received a couple of PMs with offers already, from users trying their luck.
On the other hand, it's also good to keep in mind that anyone buying such an account would most likely use it to scam (signature campaigns, probably the reason behind most account sales, don't usually pay more/substantially more to Legendary members, when compared to (the easier/cheaper to obtain) Hero members).