True enough, there's also the technical aspect to consider, as these FPGA systems are very complex and so it must have taken many years to develop each of these cores in turn.
Obviously, as the systems they emulate get more powerful and complex, they also get more difficult to develop, and thus take longer to produce.
However, as someone who chose not to buy an NT mini due to the expense, I would definitely be in the market for a cheaper, slimmed down offering of the same system. Make it out of plastic and take out the DAC, and shave a hundred or so bucks off the price, I am sure they would find a hungry new market for that product.