The user-defined literal _ms here is confusing and easy to misinterpret. The literal values (e.g. 435.38) are calibrated measurements in nanoseconds, and the _ms suffix is meant to indicate the conversion target (nanoseconds → milliseconds). However, when reading the code at the usage sites:

const CostCoefficient CostEstimator::fetchFilterIncrement =    CostCoefficient{CostCoefficientType{435.38_ms}};

...it naturally reads as "435.38 milliseconds", which is the opposite of what's happening. We should rename the suffix to ns or ns_to_ms or something similar.