Here are my valuations:-

For a non exec club member I would value CE at between £50/75 to £100/£125 with the first set of numbers representing the 80 and the second set the 160 tier point routes. The later part of the pair is if you need the extra luggage. The benefits for this customer are clear. In addition to the empty middle seat, they have lounge access, food and drink on board and fast track.

For a Blue or bronze member I would add £10 - £20 for the extra tier points earned

For a silver member the value drops to £20 - £30 as the only benefits are the extra Avios and on board food. But chances are you will have less room as you may be able to snag an exit row in Y.

For gold I’d add a tenner to the silver value for the chance of snagging row 1.