Increasing of prices

Two customers wish to have an option of increasing prices. One of them gets new price lists from his suppliers. We have an option to import products from an excel sheet, but only if items are not in the lists. How could it look like in cases for my customers?
Thanks for any ideas.

There is the Update Price List button in the Line Items of the Purchase Quote document that allows to update price list marking up vendor prices. Does this help?

It could be fine, but they will get new price lists from their suppliers in excel format, so input manually is rather a lot of work. Is there another possibility similar to items import?

Again, you can use the Purchase Quote. There is the "Import XLS" button in the line items. You can import the price list there, and then markup prices.

Or you can develop your own price list import function (using the examples for the "Import XLS" and "Update Price List").