Interestingly, unopened packs seem to fetch a fair amount, certainly more than their “expected value”, which aligns with my experience trading loot boxes on Steam.
Yeah it's a phenomenon seen in a few different CCG markets actually. Roughly 2 years after a set's release the Sealed box price and the EV start to drift apart.
Before the prequels, it was relatively easy to meet many of the Star Wars actors. I met Peter Mayhew and had him sign my Star Wars: CCG Chewbacca card at a comic convention. A lot of people seem to comment on what a nice person he was to meet, and I completely agree. David Prowse was less obviously likeable, but was also interesting to meet.
If you have an EV of £20 for the contents of a random pack and can buy them for £10, it makes sense to buy as many as you can to open and sell on the contents.
They don't have to be opened, but if the difference is large it would make sense for people whose only interest is in getting a return to buy & open them.
That all packs with price less than their EV get opened makes sense. At the same time, packs with price more than their EV don't really make sense - it's better to just buy singles in that case.
But to me, the comment meant that packs with worth (total value of their contents) less than their EV i.e. underperforming packs were guaranteed to be opened, so the EV of remaining packs would rise, justifying the price increase.