Yeah, I was just going to say that you can do that to kill bossess not just grind gold.
Also, I was terrified of the prep penalty but decided I was being stupid and went and tried it out. Thing is, if you take one level of poison it lessenss the penalty (it evens out in terms of piety gained after 15 kills but you're taking smaller hits). And what it actually does is reward good play - if you slow stuff down you can harvest popcorn for a net worth of 7 per pop (if I'm not much mistaken) 5 + 1 (slow) + 1 (poison). Since you can also sink gold into piety it's not that hard to just ride him to victory (especially if you desecrate another altar / find pactmaker). Without a slow glyph it's just a matter of leveling up (not that hard with fireball and getindare), and then you harvest for 6-ish.
When you come down to it the penalty pretty much just reduces his piety gain and forces you to play more like a TT worshiper than just any random shmoe who wants the dodge, the edge and a bunch of gold. It's not that terrible.