Transfer them to United and get a Polaris class ticket to Europe. That's probably the maximum value.
In terms of retail price per point, sure. I'll take your word for it. Seems like all the "travel hacking" blogs mention how you can get some ridiculous "value" by redeeming points for first-class airline tickets or four-star hotels.
However you're still paying significantly more points for a business class ticket than you would for a regular coach ticket. How many coach tickets can you buy for the number of points you could spend on one business class ticket? Is the bigger chair worth it? I personally tend to lean toward no.
Transferring to United is a great value. You can find 30K point fares each way to Europe.
I just did a search on the Chase travel portal for tickets from SEA to LHR on arbitrary dates in March. The cheapest itinerary was 41.8k points round trip, 20.9 points each way: nonstop on the way there, connecting in Amsterdam on the way back. I could definitely see there being certain dates and city pairs where an airline could give a better deal than the Chase portal. It probably pays to check United mileage redemption availability before booking through Chase directly, but I wouldn't preemptively transfer to United on the assumption that it would be cheapest.