I have never had a set of Talley's that were properly mounted, and the screws properly torqued, break or fail. But this is limited to my experience, and of that while working and mounting scopes on customers rifles in local gunstores. Cannot speak for those that mounted their own, and what practices were used in doing so.
Yes, Talley had some issues in the past with alignment, but aligning rods and some elbow grease took care of this. (This before Leupold Backcountry's were available)
I can definitely believe that better quality materials, fit and finish will cause an increase in price of manufacturing. If Leupold is doing such, my experience would push me towards investing in the better quality product. If the screws are suspect, improving to the larger screws would also be a consideration. But again, torquing to proper spec is paramount.
If you are spending big dollars on a rifle and scope, why wouldn't you invest in better quality mounts to ensure a more secure mounting of said optic?
It is what ensures it stays aligned securely to the rifle, and ensures that bullet can be placed on target accurately, when the shooter does their part.