Why can't I add a product? I need to add product via services, but I have strange issue with a price field.

The case is that all fields saved correctly except price field amount and it returns: 


  The requested URL returned error: 500 Internal Server Error : An error occurred (0): Unable to get the data property amount as the parent data structure is not set.


The url which is used: endpoint/product.

Here is the code:

fields `$node_data = array(
  'sku' =&gt; 'sku1',
  'title' =&gt; 'product title',
  'type' =&gt; 'product',
//  'commerce_price_amount' =&gt; array('amount' =&gt; 122.000, 'currency_code' =&gt; 'KWD'),
  'commerce_price_amount' =&gt; 12.000,
  'commerce_price_currency_code' =&gt; 'KWD'
); 12.000,
  'commerce_price_currency_code' =&gt; 'KWD'` 


which successfully added all fields except price.

I think it relate to price field format.
It works with me after disable some modules related to commerce like payment, order, cart, tax and then clear cache products saved.

I still didn't know the reason for that error