I paid my Otus 4,000 US$, which, as far as I recall, it is closer to 3,000 Euro. Isn't that more that twice "cheaper"?
The Otus is $4k, the S 70 mm standard lens is $6k at B&H. That's $2k difference and for that you get weather sealing, auto focus, auto diaphragm, a larger image circle (54 instead of 43) provided you have an S camera to put the lens on, of course. (Damn why doesn't Leica make a smart adapter from S to CaNikon and Sony FE mount)
You loose the Otus' f1,4 because the 70 mm is f2,5. Some see the Otus is the best thing since sliced bread, but believe me, the 70 mm is one hell of a good lens. To each his own.
Edit: I forgot, for $6.000 you also get a leaf shutter, if you don't want/need that it's $5.000. That's a mere $1k difference with the Otus.