I don't know anything about Topeka but I'll just assume everything depicted here is historically factual and that God designating a random uber driver as His prophet is an everyday occurrence there. Topeka sounds like a bomb ass name though.
This game really took me back to when I was obsessed with playing that japanese crazy taxi clone on PSP. Prices seem steep at first, but if you invest in the multiplier early on or focus on becoming airborne and getting the moneybags, you'll get things done a lot quicker.
It did crash on me a couple times, so you're probably better off buying just mult and boost if you want to beat the game and go for the less practical upgrades in another run.