i have a table big_table( a int,b int, c varchar2(100));

it have 1M rows.


when i run explain plan for
insert into big_table values (1,1,'whatever');

the plan table look like
--------------------------------------------------------------------------------
| Operation | Name | Rows | Bytes| Cost | Pstart| Pstop |
--------------------------------------------------------------------------------
| INSERT STATEMENT | | 1M| 17M| 540 | | |
--------------------------------------------------------------------------------

the cost is 540.

but if i run same DML on some small table the cost is much cheaper.

why so much different? if the cost is reasonable bigger, i can understand, but not so much.