Haven't considered that :/ I would have to ask around to see if there is significant interest enough to merit the engineering costs to make a cheaper version :/ Thanks for the input though!
Combined isolation and masking is a great feature! You might consider working with the author of Noise Machines[0] for a later iteration. That site is a lifesaver in a noisy office.
[0] http://mynoise.net/noiseMachines.php