Hello,
I see there are some hooks but let me just simplify it with core solution for now:
Open oc-includes/osclass/controller/search.php and go to line 586.
Add price to item array by changing this
$itemArray = array(
'title' => osc_item_title(),
'link' => htmlentities( osc_item_url() , ENT_COMPAT, "UTF-8"),
'description' => osc_item_description(),
'country' => osc_item_country(),
'region' => osc_item_region(),
'city' => osc_item_city(),
'city_area' => osc_item_city_area(),
'category' => osc_item_category(),
'dt_pub_date' => osc_item_pub_date()
);
to this
$itemArray = array(
'title' => osc_item_title(),
'link' => htmlentities( osc_item_url() , ENT_COMPAT, "UTF-8"),
'description' => osc_item_description(),
'country' => osc_item_country(),
'region' => osc_item_region(),
'city' => osc_item_city(),
'city_area' => osc_item_city_area(),
'category' => osc_item_category(),
'dt_pub_date' => osc_item_pub_date(),
'price' => osc_item_formated_price(),
);
Then in oc-includes/osclass/classes/RSSFeed.php use
echo '<price>', $item['price'], '</price>', PHP_EOL;
to output the price.
Regards.