As long as you can hire 300 total times it'll be fine. So do the highest price that you can still afford (it'll be faster). Price increases by 5% each hire; so the formulat for ending price is: endprice = startprice * 1.05^numberofhires . Remember bedmas/pemdas
Do the math. Each hire increases price 105%. That's what (price)(1.05)^300=end price. E/p=1.05^300 e/p=2273996.129 or 2.3mil Insert value for e such as 5bil 5,000,000,000/p=2,300,000 5bil=2,300,000p So for 5 bil p=2174 If you go too much less, there is less efficiency.
Remember, the lowest it goes is 10k so only higher transfers will work that well. Let me crunch some numbers.
I've run numbers in a spreadsheet, (I'm an actual mathematician) and determined the expense ratio levels off at approximately 34.38%. What this means is that for every 10,000 gold you lose during the volley transfer procedure, 6,562g goes to the person you're transferring to, and 3,438g gets lost forever. Will probably follow-up over the weekend with more detailed explanations of calculations.