There are only so many people you can reach and sell to within the niche. Thus, its income production potential is capped somewhat.
However, most of those who succeed in niche marketing are able to produce income equivalent or exceeding that earned by those working in larger markets.
They may not have as many potential buyers at their disposal, but they make up for that fact with a higher sales percentage.
If you are considering duplicating a successful Internet marketing strategy, familiarize yourself with the ins and outs of niche marketing.
If you can find the right group and offer them the right product, you can produce a very healthy income within a niche.