3K is reasonable for a confirmed business seat, lie flat, for a 10-11 hour flight. I think LH soft product is much better but UA's hard product is better on the SFO-FRA flight.
The problem with buying W and waiting is:
1. Your upgrade will not clear
2. You don't get the extra EQMs
3. If there is aircraft change (unlikely but may happen) then you have a better chance of going back to Y with a very expensive fare
4. You may be upgraded at the last moment and you get one of the crappy middle seats in the lower cabin. This is my biggest problem with waiting for an upgrade to clear.

Last time I did this segment I bought a cheap flight, upgraded with miles and co-pay way in advance since it trumps GPU; at that time the price was much more than $3K