The "Blue Back No Number" versions (without number) are considered from the very first print run and are the rarest, per PSA CardFacts historical data
At the same time, Scam can also grind reasonably well with Tourach, Seasoned Pyromancer and Kolaghans Command
Note that I'm going to discuss only sets for which I was lead designer (Tempest, Urza's Destiny, Odyssey), as these are the only sets for which I have early design files
The demand is clearly there, but there may come a point where the hype of Pokemon TCG dies down again and prices of the cards drops dramatically due to the huge amounts produced
And when I see a brilliant one like this Skylcave Shade it bums me out a little bit for a missed opportunity
She's a one-card toolkit of options, and is still one of the best planeswalker cards to have ever been printed