Data Grid

I'm not sure if there is a way to do this without using a programming
language/function ie a for loop for example. Ideally I would like to do
it all in postgresql

I have 2 tables, for example:

Item
====
id
name
cost
sold_date
item_type_id

Item Type
=========
id
item_type

Now I want to make a report whereby I sum the cost of each item type per
month (within a range) so I end up with the following:

01/04 02/04 03/04 04/04 05/04 06/04 ... etc
item_type A
item_type B
item_type C
.
.
.
etc

THe problem is that I don't know how many item types or months I need to
do it for (obviously it will be for all item types in the item type
table, but could be for 1 month or 100 months!). The only way I can see
of doing it is summing the total cost per item for a month, then
repeating that query for each month in the actual application is this
correct or is there a way to do it natively?

Many Thanks

Jake