Following up on Friday’s news that Apple has yet to give third-party accessory makers access to the new smaller dock connector on the next-generation iPhone, iLounge has some more disappointing information for consumers today.

According to the site’s sources, Apple will be the sole seller of a dock connector adapter that will allow the new handset to work with 30-pin docking accessories. It is unknown when, or even if, third-party manufacturers will be allowed to release adapters.

And that piece of plastic apparently won’t come cheap. One adapter will cost consumers $10 and a pack of three will be sold for $29. Apple will also be selling USB cables with the new dock connector for $19.

That’s definitely a scary proposition for consumers who often turn to less expensive iOS device accessories that work just as well as the Apple-branded products. Some sources told iLounge that this could be the beginning of a trend:

Some developers fear that Apple will corner the market for both the adapters and cables, much as it did with MagSafe connectors for MacBook laptops, using licensing agreements and threats of lawsuits to prevent less expensive third-party solutions from coming to market.

While $10 doesn’t exactly sound like much, the revenue could roll in very quickly for Apple. If one dock connector is sold with each of the 10 million new iPhones expected to be moved in the first week of availability, that’s a cool $100 million for Apple, with most of that being pure profit.

The next-generation iPhone, widely expected to be called the iPhone 5, will be introduced at an event next Wednesday in San Francisco. It is expected to be placed on sale nine days later on Friday, Sept. 21.

Source: iLounge