In more recent versions, these ratios (and they are simply ratios, that is, number relative to each other as you point out) are configurable, and YES, you should configure them to the best of your knowledge of your environment:
1> sp_configure 'cost'
2> go
Parameter Name Default Memory Used Config Value Run Value Unit Type ------------------------------ ----------- ----------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -------------------- ---------- cost of a cpu unit 1000 0 1000 1000 number dynamic cost of a logical io 2 0 2 2 number dynamic cost of a physical io 25 0 25 25 number dynamic
In older versions of ASE, you can use "dbcc tune(wlogical | wphysical , <n>)", but these settings weren't persistent across ASE reboots, so had to be done every time you start ASE.