The Marketplace

I'm wondering what kinds of things are being sold business-wise in the Marketplace.

Assume I own a business. (I do not).
To sum up my question: what's the best kind of business to make money in the marketplace (if any)? Should I even bother with Marketplace to offer my products? That is to say, what are typical products that actually sell, there? I don't really see a point to using it -- it looks like a bunch of things that never sell, but a few specialized items that get sold quickly and for a lot of money.

If I were to own a business, for example, in web design, how could I use the marketplace as an advantage over individual clients with specific requests, instead of designing something, then either selling it in the marketplace? Here, for example. I'm not 100% sure, but I don't think many things are purchased (if any) this part of the marketplace. I'm only basing that based upon the fact that his or her product has been available for quite some time but he or she has no "Reviews" there. Perhaps his product is purchased quite often, just that no one leaves reviews there.

[Edited: found a typo]

 

really you don't know what kind of your services?