Sweden here! ~$0.85 for a 50g letter within the country, ~$1.7 for the same overseas. Price grows with weight, of course.
Doing parts of the actual gameplay, and not just meta-info (if even that) online sounds like a "bad idea", I think. Less unique, less fun, less impactful.
Regarding the different price tiers... If the game is planned out in some manner, perhaps an estimated cost of potential packages could be decided and stuck to, and then included in the initial cost? That way, everyone's equal, albeit with a bit more work and planning on your side.
