Well, I suppose there is always a bit of inertia in any game, and even in Splinterlands your Gold-Foil Corrupt Pegasus might not sell immediately.
But inertia due to a not-so-liquid market in places is an acceptable limitation in my book, because it's largely circumstantial. Developers deliberately aggressively locking in money is definitely not acceptable in my book ;).
And the price appreciation of Splinterlands cards has been downright nuts! Only back in June I recall buying an unpopular Golden Wave Runner common for $0.30. And even that card more than doubled in price now!