Are 5 dollar battlechests heavily monitored, since only botters know how to access those. Are blizzard using them as lighting rods to draw botters out?
Not at all. The payment department and GMs are usually not directly connected, so I doubt they have any real coordination in this therm. Even then, the 5$ battlechests are not directly linked to botters at all! Since the most botters technically bot on their main accounts, which are created years ago. These of the botters who do it for profit are not the majority of the honorbuddy users, the casuals are!
5USD for US Code: https://us.battle.net/login/en-us/?ref=https://us.battle.net/account/management/upgrade-wow.html?promo%3DclassicFS5dol&app=bam&cr=true I don't know why exactly you deduced only botters know about this because its so widely spread on the internet that I would think lots of people use it, besides botters.
I think this link still works https://eu.battle.net/account/management/upgrade-wow.html?promo=classicFS5dol and if i can remember the price is 4 eur
For EU prices, don't bother with trying to get any old links working, just level a starter account and when you get to 20, log out. After a short while, when you log back in you'll get an "Limited Offer" to upgrade to the full version for half price, I've had this on every starter account I've ever got. edit: you may have to wait overnight, I can't remember. I'm not sure if this is the same on US servers.
Was just wondering, when using the link and paying with a VISA that's used on your main account (Name/Billing adress etc) does it increase the change of getting flagged? Any experiences? Or is it safe to go nuts and just keep buying the 4 Euro BC with the same card?