sum of values from an array with duplicates

You need to force a cartesian join on the tables and you can do that like this:

select
    sum(yt.price) as TotalPrice
from
    yourTable yt
        join (
            select
                11 as ID
            from dual
            union all
            select
                35 as ID
            from dual
            union all
            select
                35 as ID
            from dual
        ) sel
            on yt.ID=sel.ID

You create a subquery that has multiple records for the IDs you want and join it to the actual table you want to pull the data from.

The other thing you could do would be to pull back the individual item prices and sort it out in an array/object where you can do the maths to get the price in a much more detailed manner.

The other thing you could do quite simply with an array (or however you are storing your IDs that you want to tally the price for) would be to do a variable amount of unions inside an outer query - similar really to what is above, but will look very different:

select
    sum(sel.price)
from
    (
        select price from yourTable where ID=11
        union all
        select price from yourTable where ID=35
        union all
        select price from yourTable where ID=35
    ) sel

It's pretty much the same but depending on the rest of the columns you pull into the query, might maybe suit better.

You need to do this using a join. The where clause does not increase the number of rows. So:

select sum(price)
from (select 11 as item union all select 35 union all select 35
     ) i join
     prices p
     on i.item = p.item;