In a sandbox game you can craft, you can manipulate the market by embargos, dumping on the market, can fly capital ships, can construct your own items, weapons, ships, etc.
Right now the market value barely changes, even with a ton of money used to move product. I understand that this feature is supposed to become more "sandboxy" later on, but it isn't now.
ED is similar to sandbox games in that it doesn't have a predifined objective and that trading will be open ended. However, you are not ever going to meet more than 32 players in your game, so you can't really do massive pvp the way you can in a true sandbox like EVE.
Until ED fixes the market to make it more reliant on players, adds crafting, custom weapons, custom ships, allows players to own and operate sectors of space, etc, there is no way to consider it a true sandbox game.
At most ED has a few sandbox elements - you can be a pirate, a trader, an explorer or bounty hunter.
But that's only 4 things to do! More like 3, if you consider the fact that piracy and bounty hunting both involve practically the same thing: combat.
At this point, ED is more of a space combat simulation with some trading. Exploring is one small sandbox element, but not enough to make this game a true sandbox.
Wish it were a true sandbox, though.
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After reviewing the discussion here, it seems the problem is in defining what "sandbox" means. I posted the following definition somewhere in this thread, but here it is upfront for newcomers:
Sandbox is a genre that is not a boolean (neither simply "true" or "false"), but it is a collection of features, which when weighed in total, demonstrates HOW MUCH "sandboxy" a game is, in the SLIDING scale of "sandbox-iness".
For example, if a game is open world, that's +1 to sandboxiness, if it also has crafting, another +1, etc.
This way everyone's definition of sandbox is included, no one is left out and we can analyze how much a game is sandbox like, instead of whether it is or is not a sandbox in the absolute sense.
Hopefully that can get everyone on board to analyzing ED and move away from fruitless debates on what constitutes sandbox.
Applying this definition to Skyrim:
Open world: +1
Crafting (limited but it's there): +1
No physical limitations of where you can travel (no invisible glass walls, as for example, in Elder Scroll Online!): +1
No class restrictions (that is, are not forced to choose only warrior OR mage OR thief, etc): +1
Good/evil/neutral choice: +1
Total points: 5 points.
Applying it to Advanced Dungeon and Dragons:
+1 to everything:
Crafting, no physical limitations, no class restrictions (in latest DnD, I believe), limitless character choices, etc. You get the point.
Total points: +infinity (because it's not a video game. I'm just using it as a demonstrable example of an extreme)
Apply it to Eve:
No physical limitations: +1
Open world: +1
Crafting: +1
good/evil/neutral character role playing: +1
can build ships that signficantly impact universal politics: +1 (I want to give this a +10, but that's my personal bias!)
Completely (or almost completely) player driven market: +1
Meta-gaming (such as making alliances, secret alliances, playing politics within player groups, etc): +1
Player owned and controlled empires: +1 (again, deserves a +100 in my opinion)
Can pursue variety of careers/roles: +1
Total points: 7
Apply it to ED:
No physical limitations: +1
Open world: +1
No crafting: 0 points
good/evil/neutral character role playing: +1
No player driven market (only a slight influence): 0
No player empires: 0
Can pursue 3 careers: +1 (combat, trading, exploration only... don't think it deserves a +1 when compared to other games' career paths, but will give it 1 point anyways)
Total points: 4.
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In any case, this isn't a comprehensive analysis of all features of each game, it's only an example of how to do the analysis without bickering over definitions.