With the first chest, the best thing I got from it in 2 or 3 tries was a healing potion, which I needed to use anyway to survive getting there and back, so I ended up skipping it. The chest at the far side is easier to get to, and I got a fairly nice enchantment formula (I think maybe a highish level damage or life line). I was convinced the chests must contain something of value, being hard to get to, so was determined to get something out of one of them (the second kept offering me potion formula I already had or enchantment formula I wouldn't use, but after 6 or 8 tries I got something decent.... though I think I found as good or better of the same type of formula not too long after that).