My two cents:

If you're flying TATL regularly, I flipped my departure last summer and it drove down the price significantly (typically ~$2K/segment) to a "reasonable" $4.5 - $5K . Most of the "secondary" cities seem to go on sale pretty regularly (~$1500 each way)

AMS and ZRH have consistently been the cheapest options--my final destination is CPH, so I book a separate SAS ticket which ranges between $100-$250 USD/direction.

FRA (876) and LHR (848 and 858) are consistently expensive and full.

AMS, ZRH and DUB have been the easiest to e-up in advance-- there is no Star Alliance lounge in DUB however. (CDG also seems to have space but the connection doesn't work for me so I'm not familiar with it).