So, for games like this, I like to make progress.  But the way the game is balanced, I will never make progress.  
I could kill bad guys in 5 hits.  I spent the equivalent upgrade money of the mext archer upgrade on increasing gold, meaning that I now kill in six attacks of the archer.  And by the time I get enough money for the next upgrade, I'm at exactly 6 attacks again.
No increase possible.   I like to be able to increase at some point, but the price points keep it just out of reach.  Maybe if I spent no money on increase speed and less on clicks...