I think the issue here lies with the deposit. I wonder if the deposit is also the right to buy something for that price since there is no sales agreement. Just the intention to buy. However, if it would be non-refundable that would make it different. If there is a sales agreement then it would be with the distributer, and he has to pay for the increase or there is a statement somewhere in the text that they are not accountable for these price increases and can charge that directly to the customer. You do not buy from Stern direclty and the prices on their webpage are suggested retail prices.
I think it is up to the manufacturer to decide what price to ask for the product. And up to the distributor what charge the client. Lame thing from Stern is just that they keep postponing the run. It would be better to just make a run and sell those machines for the price they want to ask for it at that time. The distributors would only keep a list of interested people not taking any money. I also do not think the downpayments all went to Stern.
I think we will see more of these price increases, they run a title for over 3-4 years now, do not expect them to sell for the initial price all the way. Things are getting more expensive and since there is no real competition for Stern, they could just do this all the time. Once a mayor competitor comes in, things will change and we will see Stern get more efficient.