I took a ~20 minute 12km taxi ride just last Monday, and it was about €22. That's in Ireland. Considering fuel, the drive back for the driver, and that taxis have a lot of downtime, that seems like a reasonable price.
You live in Netherlands according to a recent comment; I can't believe taxis are almost 4x more expensive, unless you're stuck in traffic for a long time, but then your burger can't arrive in 30 mins?
And free delivery on €6 food item is almost certainly netting them a loss.