How does the optimizer decide whether or not to use parallelism when the parallelism threshold is specified in seconds (on specific hardware, see below) but the estimated CPU costs are supposedly unit-less? Is the estimate treated as if it were seconds or is there a conversion happening internally based on some hardware metrics?
From MS: cost threshold for parallelism Option
The cost refers to an estimated elapsed time in seconds required to run the serial plan on a specific hardware configuration
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