I use Salon Iris version 6.0, I want to update my ...

First, I'm not familiar with that specific program, but if the range of items is rather small (less than a 100) it might be easier to just do it once and get it over with.

If these is more than 100 items or you don't have time to do this change you might be able to do something else. Most of these program run on top of a database which stores all of this information.

If you know someone that knows a bit about database programming and can gain access to the database, that person can easily update anything you want (just be sure to make a complete backup before you do any change).

A range of items?  You can export the products to a text file then use excel to increase the values and then import them back in overwriting your current list.  And if you want to just update items from a certain make you can use Excel's sort ability.  Pretty straightforward.  Import/Export option is there and is great with just a little computer skill!