I would think the potential is lower in Dota2 than it was at TF2's peak for now but is growing fast. TF2 benefitted from a relatively small amount of cosmetic items to buy (they came out relatively slowly) and cosmetic drops were and are very rare so the income potential was high in favor of people that could get their creations into the game. Less competition from items, so to speak.
At present there are 464 hats and miscellaneous items in TF2 and that took 5 years+. There are already 503 in Dota2 and the store has only been open for 6 months. I would not be surprised to see it hit 1,000 by the Fall. This presents a unique scenario because the more items that become available, the less likely it is you will be able to complete a full set of anything in a reasonable time frame. Buying becomes the only realistic option. In TF2 you could wait a week or so and get any item via drop...but it has grown increasingly difficult in Dota2, and it will only grow more challenging. In that scenario, I expect that those skilled enough to make outstanding sets (like Anuxi) will be in the best position to get sales directly from the store. Also, the item creation process feels more transparent and community-generated than ever thanks to the direct integration of the Workshop into the Steam client. It makes it easier and more enjoyable to buy from the store because you know you're supporting someone in the community, like Anuxi. That said, item sets that don't look as amazing will find it increasingly difficult to generate money as they are outshined by the fancier sets. People will just take items from those sets as they drop or trade their duplicates in for them, rather than purchase them.
Also, Dota2's store items don't suffer the stigma of TF2 store items in that there is no crafting system in the game to drive down the value. In TF2 store-bought items were limited in what you could do with them, and them not being able to be used in the crafting system to make new items drove down their value. There is no such system in Dota2, however, so nobody cares so people happily buy, sell and trade store-bought sets and items. That's good for Dota2 and apparently a lesson learned from TF2.