Scry also gets much better the more context dependent your cards are. If you're deck is all cycling lands, goblin guides, and putrid leeches, and your opponent's deck is all basics, doom blades, and dark betrayals, (let's say, with an aetherling somewhere in there
) then they will value scry way more than you. In fact, in that kind of scenario, scry 2 or 3 is possibly better than draw a card, since such a high percentage of your cards are blanks.
So really, it seems like if we want to figure out when Scry X=draw a card, we need to know more about how you value the cards in your deck.
In the simplest case, we have a 50-50 split, where half the cards in your deck are worthless, and by extension, the other half are worth "two cards" each
Thus, scry 2 has 4 equally likely outcomes: a. two good cards, b. good-bad, c. bad-good, d. bad-bad. these correspond to:
a. draw 0
b. draw 1 (but somewhat worse, since you don't "draw" the extra card until two turns later, when you would have been hitting the dead card)
c. draw 1
d. draw 2
Average: draw 1 (but a turn slower 25% of the time)
This doesn't take into account the extra information you get from scrying, but that's much more complicated.
So in this super simple case, scry 2 is almost equal to draw a card, but obviously decks aren't made up of half 2 for 1s and half blanks (although it sometimes feels that way in topdeck mode).
Ultimately, the value of Scry X is going to depend on the variance of your draw step, the less variable your card power is, the more you want draw, and vice versa.