I think a cheaper way to figure out how ready you are for primetime is to submit your site to Hacker News. It doesn't cost a penny.
I appreciate and agree with most of your comments, but saying that $250 is a cheap price to learn the ropes seems wrong and somewhat predatory to me. I think you should spend time polishing your value prop if you have to fall back on this sort of rhetoric.
I think I'll follow pg's advice.