You're on the right track
But I don't think that milling speeds scale proportionally to dollars spent as tightly as you're imagining. Yes, you can take heavier cuts with a bigger and more rigid machine with a more powerful motor. But if you're using a small endmill in hard materials, the speed of the spindle might be more important than horsepower, and there will be a certain upward limit on the amount of material that you can take off at a time (expressed as chipload per flute).
That's what determines the feedrate, not the capability of the machine to go faster, or its price. However, there are various "High Speed Machining" techniques for boosting feedrates, either by increasing spindle speed and taking lighter cuts, or by optimizing heat transfer with coated carbide cutters and carefully calibrated feeds and speeds, so that much of the heat is removed with the hot chips that are flung out. Here's a section of Modern Machine Shop's site that deals with that sort of thing: High Speed Machining : Modern Machine Shop
Andrew Werby
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