You can book a one way fare in a higher fare bucket on TAP's website (see "Top Executive" fare) for ~USD900 for this flight, which seems to have no penalty at all for any changes or cancellations. Interesting...
And if you want to avoid TAP's flight, it's possible to book a itinerary like this: LIS-FRA on LH, FRA-PEK on CA. Fare would be the same.