The image is bad - it's a graph, not a grid, unless you can somehow make a negative investment. Anyway, the model distinguishes "between basic and differentiating features.. improving certain aspects only serves to maintain basic expectations, whereas improving other aspects can delight customers with less effort"
Basic features should be met because failing to do so will cost you dearly, but investing beyond meeting user expectations is wasteful: noone will rave about it.
"features that delight the user... score very highly on satisfaction and ... may not take as much investment... [but] will migrate from delightful to basic... something they expect " over time
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See also: Digital Transformation