The numbers seem high, but it actually comes out to about 12,600 isk per officer mass driver at that rate in the pic.

The reason these taxes exist in eve is to provide a sink for currency to leave the game through. Most MMOs have plenty of currency faucets but no sinks. After a few years in Everquest, for example, the average player was so absurdly wealthy that even low end drops were being sold for prices that a new player who had reached the appropriate level for the item could never even come close to affording it.

This lack of sinks wasn't such an issue before now in Dust because trading wasn't a thing, and every item you bought resulted in isk leaving the economy. Player to player trades result in isk moving, but not leaving the economy. As players start to take control over more of the economy this will eventually cause hyper-inflation, unless you put in some taxes that suck isk out. This will only really become critical if / when players start to create the equipment being sold, either through some sort of manufacturing or a loot process.