Can someone explain the gold economy to me, because it feels like upgrading dragons just makes them worse.

Take the first dragon, 1 gold every 6 seconds. At max level is 6 gold every 60 seconds. At level 1 its 10 gold a minute, at max its 6.

Add on to that that you use 4 other dragons to get it to max. Each At level 1, that could be 5 gold every 6 seconds. 50 gold every minute, instead of one max dragon doing 6 gold a minute.

Is it just that these early dragons are really inefficient and that latter ones have benefits, or is there just something I'm not understanding about the value of leveling up?