Will the economy of the universe be independent in every shard or joined?

Economy will be global and reflected in each shard.

For example, let's take a look at shops. While each shop has a local inventory (items that are currently on display), shops are restocked from a global inventory shared across all shards. If a lot of players start to buy a specific gun at Port Olisar's weapon shop, the price of that gun will rise at this shop across all shards. Eventually, the inventory for this gun will be depleted, so shops across all shards will no longer be able to restock this gun.