Using the level indicator to judge tax is metagaming, simple as that, but there are a number of ingame ways to gain the same information.
Ezample:
"Trader, kill your engines and switch to local comms, you have 10 seconds."
"Ok, Ok standing by, what's the tax?"
"I'm gonna scan your vessel and find out."
Trader scans vessel, gets readout, figures max profit per run on hold size. (Presuming the Traders hauling 1K profit per unit commodities, he doesn't think this trader's stupid) [The math's simple]
[OOC: the trader's flying a humpback, he's level 35, he's got just over 200 cargo space, the max profit he can make in any one run is 200k, taxing him 2mil is pointless he hasn't got it, his whole ship isn't worth that, he can't pay it]
"150k" says the pirate
using in game information the pirate has garnered enough information to make a reasonable tax, it's rendered the last trade run pointless, because the pirate now has the profits of that in his hold, but it hasn't set the trader back so far that he feels demoralised with the trading lark.
Taxing bigger transports the game gets a bit tougher, the pirate must then consider how much the cargo cost and how much it will cost the trader to replace it, there's no point taxing an ADV train pilot 4mil per run, his entire cargo, plus bots/bats isn't gonna cost him that much, it's cheaper for him to go splodey than pay. From an Rp point of view Interspace has got his ship insured he's out of pocket by two mil, not four. Better all round. Greedy pirate gets nothing.
The level in the corner means nothing and shouldn't be used for anything other than the greater than Lvl 30 rule for initiating PvP. It's not hard to figure out a reasonable tax using the resources you have available to you.
I thank you for you time.
Saint Del is considered a holy healer of diseases of children, but also as a protector of cattle.