Unfortunately this is what happens with an EOL (End Of Life Product), but with over 90 thousand still in stock, you should re-think your business model.
My suggestion would be to create a NEW product (or products) that incorporate the SX chip, but in Parallel, that SAME product could use a Propeller. It is very important to keep the functionality identical during this stage. This way you generate an outward flow for the SX and then when it is actually gone, you use the Propeller in it's place. Design the PCB board so that it will take either one chip or the other.
At least that way at your current "giveaway price" of $0.78 that's about $71 thousand dollars locked in assets you can't even benefit from.
The 40-Pin DIP Propeller suffers a similar fate but in reverse .... Out of Stock until September? If you expect to gain any traction, this is not the way to do it. This is not the first time this has happened either. If I was a manufacturer and was designing a new product, the availability issues would not paint a very confident picture, especially with something like Propeller2 on the end of a carrot stick ... After spending 20% of my life working at Parallax and working night and day on the Propeller2 I feel as though I have some say in this. Throw more effort into SMART R&D projects that use more of your product and inside know how than outsourcing to someone you have limited control over. Lay the efforts of R&D out in a way that they form building blocks for your current and future products.... i.e. You did this with the Basic Stamp I and II ... and avoid R&D that leads to singular products that are difficult to expand or build upon. They may be neat and cool, but don't contribute much to the bottom line and in fact can be detrimental to the bottom line.