Consider first of all, that if you do make one of these, you will still need to invest in stones. The prices I see for the 1x4 inch genuine KME stone are $25 each, so if you want all 6 diamond stones, you will spend $150. The deluxe kit also gives you 4 Arkansas stones and a loaded strop, so the $350 price begins to sound more reasonable.
Then you have the tradeoff of time versus money. Consider that the KME is a refined and proven system. This is not to say that you cannot build something as good, or even better, but it will take time and energy. These days I consider that I have a host of projects and I'm not always looking for another one.
If, like me, you already own the KME, there is little interest to 3D print a device that works like it, but knowing you can is interesting. He also prints some angle blocks which could be useful if you flip the KME guide for smaller angles, making it uncalibrated.
Tom's Knife Info / [email protected]