I’m still not sure what the best investment is in terms of promoting a product, but I can share with you some results I’ve had with PPC. I’ve used PPC in the three following ways:

1) PPC direct to Affiliate – Spent $800 last year, made $100. Bad investment

2) PPC to Email Opt-in – Spend $35 per week, make $100 per week minimum. Good investment.

3) PPC to Landing Page – Spent a few bucks, but not really good data.

I would stick to article marketing as the best way to generate sales. You can do a lot more testing without spending a penny…except for a hosting and domain name, but you don’t even need to that if you use a squidoo lens as your landing page.