Iron lockboxes are becoming unpopular, mainly because the cost of opening a lockbox (requiring a silver key) is high. From the forging of items came this idea, that there should be BRONZE keys! These can be equivalent to Silver keys (in pieces) such as the following:
A Silver Key costs 750 Energy. (can be used for any regular lockbox)
The following ideas are what I came up with:
A Bronze Key can open only Iron Lockboxes.
A Bronze Key costs 250 energy and has 1/3 chance of successfully opening the box. (optional: if bronze key fails, lock box can potentially jam the iron lockbox and render it useless - 25% chance of happening).
This way, more people can afford and are willing to open iron lockboxes.
Of course, this would probably have to coincide with a promotion that involves the contents of the iron lockboxes.
People already rage about the idea of forges failing, despite having a more costly 100% success rate option available to them. I'm not sure the idea of spending 250 energy and having it fail is going to sit well with anyone.
Making lockboxes popular again would be better done by putting new stuff in them so people would want to open them for those items.