<s:textfield id="item[ {#cursor.index}].product.price"
name="item[%{#cursor.index}].product.price"
value="%{product.price}" />
Seems to miss %
and basket.item
, please correct to
<s:textfield id="basket.item[%{#cursor.index}].product.price"
name="basket.item[%{#cursor.index}].product.price"
value="%{product.price}" />