That does factor in to our thinking but we resolve that by dividing Average Gold Gain [(Base + G-Get)* Multipler + Unit Sell] by the stamina Chr used. X/12 , Y/37 , etc. Once that is calculated you will know which is more efficient irregardless of how many times you need/want to run it.
It will probably be found that Pastoral Gate is the most efficient for pure gold gain. The Jpn Wiki says this but I couldn't find any calculations to support that statement. What we will probably end up determining is which stage you should run to get a "Fairly High Gold Gain" With Useful XP Fodder Units.
E.g.
Pastoral Gate:
Charisma Cost = 12
Stage XP (/Chr) = 123 (10.25)
Base 3* Gold (/Chr) = 900 (75.00)
No. Units Betty Can kill [Av Gold Gain] (AvGG/Chr) = 43 out of 45 [at 10% = Average of +1200 Gold for 3*] (100.00)
No of Unit Drops 5
Soldier (Bow) [3] x2 EXP:50 (55 Same Class) Sell Value 300
Soldier (Unit) [3] x2 EXP:50 (55 Same Class) Sell Value 300
Royal Soldier Hector [3] x1 EXP:80 (88 Same Class) Sell Value 500
(Don't have drop rate %'s but they could be deduced fairly accurately from a large datapool.)