[AMORO-3009] Treat read and write cost as the same when evaluating optimizing

[klion26]

Why are the changes needed?

Close #3009 .

Brief change log

• Treat read and write cost as the same when evaluating optimizing

How was this patch tested?

• [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible

• [ ] Add screenshots for manual tests if appropriate

• [x] Run test locally before making a pull request

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable)

[klion26]

@zhoujinsong could you please have a look this when you're free.

[klion26]

@zhoujinsong thanks for the review and merging!