Avoid updating purchase price with new transactions?

Hello FA team:

I need persistent purchase prices for all of my inventory items.

To prevent the auto-updating of purch_data.price when entering an invoice or grn for an item, I commented out the function calls to add_or_update_purchase_data in:

/purchasing/includes/db/grn_db.inc
/purchasing/includes/db/invoice_db.inc

Seemed to do the trick, as I can still change my purchase prices from the /inventory/manage/items.php? page.

If anyone can tell me if I've broken anything that'd be swell. I grep'd for more calls to that function but don't see it anywhere. I also don't know if purch_data.price is used for anything but prefilled info.

Insights would be very helpful. Thank you for the cool project.