I tested it here before I posted my first solution for you, and it works fine for me.
I can in phpMyAdmin that my products_price field is correctly updated with the new prices for me.
And then in my store if I run Admin->tools->store manager->reset products price sorter, my storefront will also show the new prices correctly.

So something must be wrong with your data. Perhaps your itemnumber values don't properly match your products_model numbers. Mismatched itemnumber-vs-products_model would cause a 0 price to be entered.