Your $30.00 will result in a quieter Makita trim router. But it will still be a trim router at heart, It was never engineered for the heavy duty usage that is typical of CNC carving. A trim router was engineered for intermittent usages, like flush trimming laminate or easing an edge with a round-over bit.
Let’s look at the engineering that was applied to each product in order to meet it’s targeted use. In the trim router the motor uses brushes, the spindle does not. The router uses a simple collet system designed to hold router bits. It can have a measured runout of as much as two or three thousandths of an inch. The spindle uses a more precise collect, shaft, and nut system yielding runout measurements of less than one thousand of an inch. The shaft and bearing systems are totally different. The router has a simple single bearing on each end. The design of the spindle’s shaft is more complex in order to support groups of bearing. Even the builder user class spindles have 5 bearings.
All of these differences result in a quieter, smoother running machine. Capable of better supporting the cutting tool, and this results in higher speeds and feeds, less chatter, better finishes, and longer tool life.
After all what led us to purchase a ONEFinity. It’s a more ridged machine. To me a spindle is a natural evolution in the perfection of that rigidity.