----edit---This is a mathematical discussion.
No its not, since you lack data to make it one. You are ignoring factors that are part of the equasion making it absolutly pointless.
It is also not a "mathematical discussion", because its fifth grade maths you are talking about here and calling it a mathematical discussion is really a bit much for that.
edit: just so noone cries about me not backing up my point:
You can't even start with 50g/min because it doesn't work out that way. The first gold "tick" is about 20 to 30 seconds into the round and the last tick is hard to pin down, because of the randomness of fights ending. It might be less then a minute overall or more --> we would need statistical data for that. If you now think this is an unimportant point then look closer and calculate how many gold ticks per round you will get and how long rounds take on average, especially taking the fact into the equasion that you have servers with fewer players, thus making the individual rounds shorter or more random. Then take siege mode.. where you will have different chances for defenders and attackers depending on the map you play on. Not to mention that you have this same problem with the battle maps. Then you can start on thinking about autobalance and joining ... people who only play for half an hour at a time have a much better chance to enter crap teams since when you initially join a server you will end up on the team that lost the last round in most cases ( also would need more data to really look at that factor)...... and so on... there are so many things manipulating your "mathematical diskussion" wich you just ignore, so your calculation is pointless.
The only thing that will solve this problem is not a mathematical equasion but collecting data and seeing how it will work out once the extremly rich and older players have used up all their horded gold. There are players with so much gold they can probably play a month as full tincan without running out of money.
If you just started playing the whole thing feels very balanced and not "to easy".
And let us also not forget that since we are talking about balance here it is not enough to calculate the possible upkeep. Things like people buying and selling equipment also have to be considered if you want to make a proper point. Loosing 1/3 of the value of any item bought when you sell it also counts a lot, not to mention people collecting different sets of gear, wich also takes gold form the "economy".
Sit back and wait and look at how the balance works out over time and stop trying to create arguments with pseudofancy maths.