Saving domain name cost and seo

You will most likely get poorer seo results as your central domain is not as targeted.

Register 1 domain targeted for your first product and make that a success before you launch to your second product.

You will have enough on your plate getting traffic to 1 product first.

You've asked a question Easy Cash can't answer. There are too many variables to determine "how much poorer" you'll be by placing each site on its own domain.

My gut instinct tells me you might have to do more work SEO'ing (sure, that's a word) the subdomains than individual sites because the top level domain will have so many different topics associated with it. Someone else with more experience in the subject may come along and say otherwise. If that's the case, I'll stand corrected. I didn't mess with subdomains long.

And quite honestly, you're not looking at that much extra in costs. Domains can be had for less than $10 per year. SEO costs can range from $0 to X (as much as you can spend). One sale per year, assuming a $10 price point, will take care of the domain costs. There are tons of free and inexpensive ways to drive traffic and optimize your site. Just search here and you'll find more than you can handle.

Bob Bly, a pretty decent marketer (he's taken a few dollars on mine), suggests individual sites for each product and only to centralize once you have an established brand -- but to keep the individual sites as well. His theory on centralizing after you've established your brand is that people will be searching you out at that point and having all of your products in one site should lead to impulse sales, while your individual sites rake in cash via searches and other marketing methods.

I agree with Easy Cash, if expenses are a concern (hell, even if they're not), work one project at a time. Work the learning curve to create each new project in a more efficient manner. Why make entry level mistakes on fifty sites when you can just make them on one or two? Use what you learn to be quicker, better, leaner and meaner as you go forward.