You make a good point, however I know plenty of people who would pay through the nose to not have to hammer their 101 or slightly less dura equipment. Considering GF could charge 75 diamonds per 'Bolstering hammer' as I call it, I'm sure they'd end up generating an interest and profit higher than that of Golden Repair Hammers.
And wouldn't you pay 75 dias to raise your equipment's maximum durability up by 1?
Well, most people consider 101 or 102 dura to still be under dura. Using your suggestion, then yes, taking the item to 106-107 (max of 5 uses of the proposed hammer item) would be worthwhile *to a player*. 375 diamonds to get an item to mid-OD status would certainly be attractive.
But not to GF. And that's why we'd probably never see such an item. Not to mention that RW would have to engineer it first. At GF's request. Which isn't going to happen.
BTW, thanks

I thought it was rather clever. Just hoping PETA doesn't see it.
People for the Eating of Tasty Animals? I'm sure they'd approve.