> One programmer costs ~ 300 cores. [...] If your code consumes less [than 300 cores], you should care about productivity. Adding cores is easy while adding programmers is hard. [...] Do not make performance-productivity tradeoffs below [1000 cores].

Computing time is cheap these days, but this kind of math doesn't make any more sense than comparing feet to miles per hour. Programming time saved is a one-time gain, whereas the performance loss in continuous. Let's say you write code for a single core, you spend 10 hours instead of 20 by accepting a 50% slowdown, and manage to compensate by adding an extra core. Depending on how long this code runs, there will be a point at which the ongoing costs of an extra core surpass the one-time saving of 10 hours' programming.

If all you need is a working prototype then sure, performance shortcuts may be worthwhile. (Although you can't calculate trade-offs as suggested). But for long-term production systems they will always start hurting at some point.