My Shimano Nexus Premium 8 hubs cost substantially less than £235, as I had to buy them online (not available locally here in France). I got mine from Germany.
The £235 is an approximation I took from the OP's bill from Rohloff for repairs. I remember the wide range of prices on the net for Nexus boxes and wheels when I was shopping for them a few years ago. (Tip for those looking for a Shimano Nexus box: buy the whole wheel, buy it only with a fitting kit of rotary control, cables and brackets, and buy it in the winter when the manufacturers sell off made-up wheels not used for the assembly of sold bikes, when you can get amazing bargains.)
If I get around 5,000 kms from them I will be happy.
Well, maybe I'm just a wrecker, or maybe I was unlucky. In The Netherlands there are Shimano Nexus hubs, typically wretchedly neglected, that soldier on for many, many tens of thousands of klicks, so I wouldn't put my neck on the block with a generalization from my very limited experience with the Shimano. I liked the Nexus hubs I had a lot; in some respects, if not sturdiness, they are initially superior to the Rohloff, or at least more convenient and instantly lovable, whereas the Rohloff needs time to grow on you.
The difficulty of getting the "oil bath" Shimano Nexus gear hub service kit (and its price, twice the Rohloff service kit's price!) tells you that almost nobody actually services Nexus hubs; they just run them into the ground and replace them.
I think your scheme with the oil and the marine grease is superior, but too much trouble for me. A large part of the attraction of the Rohloff for me is how easily it fits into my no-fuss-no-bother near-zero maintenance/replacement scheme of operating my bicycle. In that perspective the Nexus hub gearbox, at least in my hands, is a consumable.