I'll throw in with Jonathan here in that the "Fast" aspect has to do with the concept-to-production timeline, not so much the performance aspect of whatever it is.

The point of this saying - though admittedly the shorthand version states it inelegantly - is the three elements are interrelated and optimizing them for any project involves making decisions and accepting certain trade-offs between them. Changing any one will affect the other two to some degree or another. The effects may be negligible, significant but acceptable or simply unacceptable for that project, but the effects are there.