The Inworldz economy wan't "robust" enough for him. He elected to return to his "Multi-million Linden business" on SL.
In my humble opinion, it takes more than a month to establish yourself and start making consistent sales. This person made a few sales so they can't say they didn't do ANY business. I got the impression that they came to Inworldz thinking that it's a world of SL castoffs and refugees, so the ready-made consumer base was here just waiting.
Ummm, not necessarily. SL is a big place, and where you might have a nice niche and make lots of dough in SL, you are not known in other quarters.
I didn't know this merchant from Adam or Eve when they first arrived. I didn't shop their wares because I didn't have need of them, but at some future date, I may have done so. As more sims pop up and more communities form, the market for their goods would have indeed expanded. It would appear that Inworldz is past the "omg hurry up and get it here because we don't have any of it" phase, so that creators aren't struggling as much to meet the demand of the most popular and needed goods (hair, shoes, shapes, skins, basic animations, etc.). This gives all merchants a chance to breathe, and start creating diverse and unique goods, in different genres, rather than just "general audience".
More and more roleplay areas are being created as well, opening up the market for genre-specific goods. This merchant sold something that would have fit better in certain genres, rather than "general audience". Chances are excellent that if they'd stuck around for awhile, their sales would have steadily picked up.
As many people have stated, in blogs and in the forums, the key to a merchant's success is knowing, and understanding, your overall market. If you just barge in and expect to have instantaneous success in a new market, chances are you won't. Unless you're a REALLY BIG NAME like Pepsi, Coca-Cola, Nike, Reebok, Folgers, etc. - people may not know you or may not know you well.
Don't be in such a big hurry to cross Inworldz off as an economy not worth investing in. We just hit 20,000 members, and that number will do nothing but grow further. People with more diverse tastes are now moving in, and we need merchants to serve them. You may not have instant success but, given time, you could definitely become well-known and patronized.
It's a combination of success, smart marketing practices, and patience.