Well from my experience so far with Armpits its been a really weird ride...

My first version: http://www.armpits.com/pits/ converted really well for me personally and did fine for affilliates but I wanted it to do better.

Then there was an intermediate amateur design that was crap for both me and affiliates (it stayed for 9000 uniques) and then was burned.

Then there is the current version, which is doing great (& I mean GREAT) for me personally but to be honest is sucking for affilliates....so to counteract that, there is a pro design coming, one being tested next week (hopefully)

I truly love and respect my affiliates, as I mentioned to one WM recently, affiliates are treated by me, the same way I treat a 1st time member....I want them to get the best possible experience, stay with me and get exactly what they are looking for and will try to go all out to acheive that.

Basic rule of business, Its far btter to keep a customer, than find a customer.

Anyway back to your question, it really does depend on niche, color scheme, traffic and how you want to be perceived....test the water and keep testing the water, for as you say $400-$800 is all you are risking & thats only 10-20 recurred memberships. If you hit it right that will be done in less than a day.

Hope my 2c is of some use....
Dave