Era's trading system

[bandoo]

**NOTE: I AM NOT COMPLAINING IN ANY WAY, I AM ASKING JUST BECAUSE OF THAT CURIOSITY...

I usually either pk or base with friends, I barely trade.

But I've tried trading for a week to sell some items and earn a Jeni Umbrella...
Since then I had some questions that were impossible to answer by myself.
So that's directed to whoever thinks that they are "good" traders.

1-Why is trochus the main currency? ( ANSWERED )
2-Why is the conversion rate between an aeroleta and a trochus 1:2 respectively, considering they cost the same? Similarly, why is the shovel rate even worse when you think about trochus as a currency? ( shovel part not answered )
3-Why do some items randomly have set prices even though they are rarer(less exist in the game) and older than others? For example an Excalibur(2011 or 2012 + expensive) costs less than a stun gun, but equal to a valentine's dagger(2016 + cheaper)...(ANSWERED)
4- Why are guns untradable?( Someone probably answered that, but I cannot seem to find the answer, if not, then it should be on the bottom section)
5-How is it possible to get a high amount of trochus(above 50k) with a realistic method(spend your lifetime digging?) other than buying an auction item and selling?

---------------------Staff members or Highly knowledgeable players------
Why can't we drop items anymore?
Why is cash ( gralats ) untradable?