id  cost  max_cpc  convertion
7    1$        1              10
6    5$        1              11
5    6$        1              14
4    2$        2              15
3    7$        3              15
2    8$        1              1
1    1$        1              10

mysql> create table test (
    -> id int,
    -> cost int,
    -> max_cpc int,
    -> convertion int
    -> );
Query OK, 0 rows affected (0.28 sec)

mysql> insert into test (id, cost, max_cpc, convertion)
    -> select 7,1,1,10 union all
    -> select 6,5,1,11 union all
    -> select 5,6,1,14 union all
    -> select 4,2,2,15 union all
    -> select 3,7,3,15 union all
    -> select 2,8,1,1 union all
    -> select 1,1,1,10;
Query OK, 7 rows affected (0.13 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> select sum(cost), sum(convertion)
    -> from
    -> (
    ->   select @a:=max_cpc
    ->   from test
    ->   order by id desc
    ->   limit 1
    -> ) a,
    -> (
    ->   select @b:=max(id)
    ->   from test
    ->   where max_cpc != @a
    -> ) b,
    -> test
    -> where test.id > @b;
+-----------+-----------------+
| sum(cost) | sum(convertion) |
+-----------+-----------------+
|        12 |              35 |
+-----------+-----------------+
1 row in set (0.01 sec)