WB only spent around $25M on the Whedon reshoots which would've been the same amount that Snyder would be given had he returned for the reshoots as initially planned.
As mentioned… we’re all just musing about hypotheticals and what-ifs. That’s okay. Indeed, it’s a pretty common activity in these parts.

And in
my hypothetical, I’m asking what-if WB had just let Snyder finish his theatrical cut? In which case, there’d be no additional expense involved with shooting/re-shooting Whedon’s new scenes (even if directed by Snyder) or paying Whedon his (likely) substantial remuneration because… there’d be no Whedon. (As we now know, zero Whedon footage was used in
ZSJL. So there
was sufficient original material available to make a finished film.) Another example: Holkenborg was paid to write the music score. Then Holkenborg was fired. Then, the (no doubt) more expensive Elfman was hired. Etc., etc. Bottom line, the Snyder-to-Whedon “course correction” didn’t come cheap.
As to whether a hypothetical Snyder theatrical cut would have done bigger box office than the Whedon version… I’m actually more skeptical about that. I think the good will (positive reviews, etc.) that
ZSJL earned was due, at least in part, to the passage of time — during which the “mythic” status of a possible Snyder Cut grew. But had that cut (or some version of it) been released back in 2017, I’m not sure that the BO result would have been any different. As
@Superchan said, the taint of
BvS (just 18 months earlier) would probably have affected the opening weekend of
any sequel. OTOH… a better movie might have had better word-of-mouth and better “legs.” But, again, this is all just speculation.
One thing we might all agree on:
ZSJL had the good luck of timing. Under the new/current WB-D regime,
ZSJL — almost certainly — wouldn’t happen.