Why would people pay you more for your products? Because you'll be providing them with more value. If you can show people that you are giving them more in terms of value (real or perceived), then people won't mind giving you more bucks for the same product.
Now, how to increase your existing products' value?
Distribute your content in different formats
You're selling a $27 e-book and making a few sales weekly? GREAT, that's more than many other marketers online! Here is how to get more sales AND more money per sale..
Covert your product in a “Bonus Audio Course”. All you need is a microphone (I'd recommend a USB microphone for best quality) and a piece of free software called “Audacity”.
Audacity allows you to record and edit audio files in the most commonly used format in the world: mp3.
What about the content? Simply read out your ebook! Make different “modules” out of the ebook chapters.
Covert your product in a “Bonus Video Course”. Same as above: microphone, OpenOffice.org (to create presentations) OR FreeMind (mind mapping software) – both free.
Create summaries in your presentation or mind mapping software, read out your product, add some personality! You'll need a screen capture software like Camtasia Studio or Jing (free) to do screen recording.
You can even sell the video course itself as the main product and give the ebook as a “bonus transcript”! That alone can allow you to double the price you charge!
Offer one-on-one consultation
It doesn't matter how good your e-book, mp3's or videos are, people will still have unanswered questions. Some of them will pay you for your time if they see you indeed have a vast knowledge about your niche. If you are good enough, you can charge $50 for 30 minutes consultation. If you're REALLY good, you can charge $500 for a 1 hour consultation.
You can include it in the package, but I'd advise you to put it as an optional offer, or offer it in the back-end, after your item has already been purchased.
Give in-a-box solutions
People just love being lazy. Provide them with ready-made materials which complement your main product.
If you're selling a weight lifting program, provide printable workout logs. Selling an AdSense course? Provide themes and templates. Giving a course on using PLR articles? Provide them with PLR articles.
The goal here is to provide more value. Provide value, and money is just a by-product!