I found the answer on Magento Forums:

https://community.magento.com/t5/Magento-1-x-Technical-Issues/Cart-price-gets-deducted-on-page-reload-when-product-qty-is-more/m-p/94352#M8113

Quoting:

Removing following from the Mage_Sales_Model_Quote_Address_Total_Subtotal _initItem() method solved it for me:

&& !$item->getHasError()

Because we do want to show prices when there's an error, we just don't want them to buy when error.

EDIT:

After inspecting a bit more, I found that the problem was that I didn't set attribute "is_in_stock" when importing products (i thought I didn't need it because "manage_stock" was set to "No"). That was the cause for get "getHasError()" returning true

I found the answer on Magento Forums:

https://community.magento.com/t5/Magento-1-x-Technical-Issues/Cart-price-gets-deducted-on-page-reload-when-product-qty-is-more/m-p/94352#M8113

Quoting:

Removing following from the Mage_Sales_Model_Quote_Address_Total_Subtotal _initItem() method solved it for me:

&& !$item->getHasError()

Because we do want to show prices when there's an error, we just don't want them to buy when error.

EDIT:

After inspecting a bit more, I found that the problem was that I didn't set attribute "is_in_stock" when importing products (I thought I didn't need it because "manage_stock" was set to "No"). That was the cause for get getHasError() returning true

I found the answer on Magento Forums:

https://community.magento.com/t5/Magento-1-x-Technical-Issues/Cart-price-gets-deducted-on-page-reload-when-product-qty-is-more/m-p/94352#M8113

Quoting:

Removing following from the Mage_Sales_Model_Quote_Address_Total_Subtotal _initItem() method solved it for me:

&& !$item->getHasError()

Because we do want to show prices when there's an error, we just don't want them to buy when error.

I found the answer on Magento Forums:

https://community.magento.com/t5/Magento-1-x-Technical-Issues/Cart-price-gets-deducted-on-page-reload-when-product-qty-is-more/m-p/94352#M8113

Quoting:

Removing following from the Mage_Sales_Model_Quote_Address_Total_Subtotal _initItem() method solved it for me:

&& !$item->getHasError()

Because we do want to show prices when there's an error, we just don't want them to buy when error.

EDIT:

After inspecting a bit more, I found that the problem was that I didn't set attribute "is_in_stock" when importing products (i thought I didn't need it because "manage_stock" was set to "No"). That was the cause for get "getHasError()" returning true