How to add a fast new SSD to your old Mac or MacBook for only $150

When I first wrote about using solid state drives (SSDs) to radically improve the performance of older Macs, high-capacity SSDs were just beginning to become affordable. Replacing a Mac’s 500GB or 1TB hard drive with a same-sized SSD required at least $250 back then, but the benefits were tremendous: even an aging machine became markedly (5x) faster, silent, and — unexpectedly — more fun to use. All for much less than the price of a new Mac.
Today, high-capacity SSDs are more a