As someone who has attempted, in vain, to grind SGbow profitably (relative to an unupped no-land stompy), let me mention that you must take into consideration that AI3 grinding gets many more spins per hour. This not only means more cards, but more +5 electrum winnings, which definitely add up.
A slow FG grinder like SGbow (which, in my humble opinion, just doesn't cut it without a good deal of upgrades) on FG's is MUCH less profitable than AI 3 speed grinding.