I believe endless copper mine is correctly priced....
Firstly I agree with Tierarzt in that you dont have to buy them and they dont give you an in-game advantage other than saving you time in rebuild activities.
Secondly I dont have any yet - but I may do at some point......
My rational for this is that for certain things there needs to be a barrier to everyone being able to find, build or trade everything - otherwise the game and its trade system wont work as everyone will have a fully self sufficient island which defeats the need to trade which is ingrained in the game culture and the need to spend hours every day with the game....
Also the gem buyer needs to feel he has an advantage or otherwise there wont be the gem sales needed to maintain the game - as has been said BB is a commercial organisation. Obviously the advantage isn't real - its about buying time or buying a shortcut to what would happen naturally given sufficient amount of time spent waiting.
Now for the detail;
According to BB- the endless copper mine is just that - it never expires unlike the gem pit.
- Also BB believe it to return its investment cost after 600 days at L1 (based on what I don't know but lets assume the logic is correct for a moment) - as we all know, no-one keeps any high value item at L1 its not cost effective so at L5 it returns its cost in 600 / 5 = 120 days.
- Many people have a buff buddy who they swap baskets with twice a day so assuming 75% of the time buffed this reduces it time to return cost to 80 days.
- If you bought the gems with a 50% free offer then this becomes 54 days as 54 days + 50% free = 81 days.
- Rather than buy the gems to buy the mine the better deal would be to buy the gem pit and use the proceeds from the pit to buy the mine - the pit returns twice its cost so therefore paying for the mine with pit gems halves the cost further so we get to 27 days.
So given the logic above it can make sense to buy the endless copper mines - especially if you buy it via gem pit proceeds that you obtained through discounted gems.
And of course all of the above only applies if you are one of the many people that support this game either by paying for gems with real life money or by paying gem goods from other players that have spent their money.
fishslice
(proud to support the game through the purchase of gems)