That was so long ago, I'm pretty sure the (then 3, counting Jeff) developers weren't even getting paid yet. Might still have been running the site on a (single!) box under somebody's desk. Was still a few months til the private beta started.

I'd imagine (since I wasn't around at the time) it was more of a choice between "pay nothing" and this, Stack Overflow had no income until after launching (ads I think were the first thing) and no funding for years after that.