I am one of your backers and think this is a great idea.
I do think you are too self-deprecating. Even the title of this topic "Another Taspberry Pi Hat on Kickstarter" implies that this board is nothing special, when it is very useful. The price is a little high, but certainly reasonable (in my opinion). But this is the sort of thing solved through economies of scale. I think people will back you because nothing else like this really exists (and they want it to exist), not because the price is "right". You are in a tough situation, though, due to the extremely low price of the Pi--I think there is some curious consumer psychology at play here. You get an entire working computer for $35, so an add-on that costs about the same will need to be perceived as providing about the same value as the $35 base product. I think your product does, as my time is valuable and your product makes the Pi much easier to use. I think you should drive this point forward as a primary selling point, as it is the main reason I backed your campaign (the first thing I have ever backed).
On a side note, I personally would use the DACs (for audio synthesis), but I don't know that I would use them at the same time as the ADC/PWM channels. I think it was wise to remove them. In the future, perhaps you can offer two boards, one DAC/ADC focused (audio/data logging/other analog), and one PWM/digital focused (for robotics, copters, other digital stuff). Just a thought.