Except staying on the edge costs exactly the same as not, when you take the resell value of the components on the second hand market into account. The problem is that some can afford to lock their capital in the hardware (via one-time investment) and some do not.

R9700 will lose less than 30% of value in the upcoming 3 years. Give or take. Yet people buy ancient cards for way more than 30% of R9700's cost.