PostgreSQL: Cost

src/backend/optimizer/path/costsize.c

/*
 *  seq_page_cost   Cost of a sequential page fetch
 *  random_page_cost  Cost of a non-sequential page fetch
 *  cpu_tuple_cost    Cost of typical CPU time to process a tuple
 *  cpu_index_tuple_cost  Cost of typical CPU time to process an index tuple
 *  cpu_operator_cost Cost of CPU time to execute an operator or function
 *  parallel_tuple_cost Cost of CPU time to pass a tuple from worker to leader backend
 *  parallel_setup_cost Cost of setting up shared memory for parallelism
 */

Default value is at src/include/optimizer/cost.h:

#define DEFAULT_SEQ_PAGE_COST  1.0
#define DEFAULT_RANDOM_PAGE_COST  4.0
#define DEFAULT_CPU_TUPLE_COST  0.01
#define DEFAULT_CPU_INDEX_TUPLE_COST 0.005
#define DEFAULT_CPU_OPERATOR_COST  0.0025
#define DEFAULT_PARALLEL_TUPLE_COST 0.1
#define DEFAULT_PARALLEL_SETUP_COST  1000.0