which admin change last price?

[lat9]

... or you could use the built-in admin activity log (Admin Access Management->Admin Activity Logs). I changed the price of one of the Zen Cart demo products $299.99 to $399.99 and then viewed the activity log. It showed the page_accessed of product.php, with parameters of cPath=1_4&product_type=1&pID=1&action=update_product&page=1& and had this in the postdata field:

stdClass Object
(
[products_date_added] => 2003-11-03 12:32:17
[master_categories_id] => 4
[products_discount_type] => 0
[products_discount_type_from] => 0
[products_price_sorter] => 299.9900
[products_status] => 1
[products_date_available] =>
[manufacturers_id] => 1
[product_is_free] => 0
[product_is_call] => 0
[products_priced_by_attribute] => 0
[products_tax_class_id] => 1
[products_price] => 399.99
[products_price_gross] => 399.99
[products_virtual] => 0
[product_is_always_free_shipping] => 0
[products_qty_box_status] => 1
[products_quantity_order_min] => 1
[products_quantity_order_max] => 0
[products_quantity_order_units] => 1
[products_quantity_mixed] => 0
[products_quantity] => 30
[products_model] => MG200MMS
[products_previous_image] => matrox/mg200mms.gif
[img_dir] => matrox/
[image_delete] => 0
[overwrite] => 1
[products_image_manual] =>
[products_weight] => 23
[products_sort_order] => 0
[products_name] => stdClass Object
(
[1] => Matrox G200 MMS
)
...

You could write a script to interrogate this information directly or write another script to post-process the activity logs that you've maintained in .csv format.