Deposit refills

I have been trying to work out how deposit refills are so expensive on TO. I was thinking of trying to run an industrial iron mine to process my gathered refills, but looking on trade I'd be better to just sell them as even when x4 buffed the iron mine wouldn't produce enough iron to cover the cost of the refill and that's not even taking into account the price of the 4x buff. Can anyone shed some light on this?

People pay for convenience. Mines that don't run out every day or 2 is more convenient than sending out geologist and rebuilding for several hours every day.

Why not just buy iron ore? If how I'm working this out is correct it would be cheaper with the added plus of not having to dig it our of the ground.

just shhh and take the money ;)