How to add a new field in Products Admin Prices

[Kanary]

Dear experts,

I'm facing difficulties understanding how the admin controllers are working and how I can edit the Product prices admin page.

For example in PS 1.4.4 to add a new field in the product admin page, you go to admin/tabs/AdminProducts.php and edit there.

But in PS 1.5, it has left tabs, so how can you add a new field in the Prices tab?

Waiting your kind reply,

Regards,