If you need to assign an special Price list to a specific client, you should do the following at the web version. Keep in mind that you need to set the Specific client (Custom $) on the setting on the device. That is at Settings > Sales orders > Orders > Discount Structure > Type > Specific Client (Custom $)

Web > Database > Products > Price list Update - Per Client

Select Per client and product individually.

• This options will let you assign a price list to client to have select 

First of all you should select a client to assign the new price 

Type the new price and then Save & Continue

You may assign the price by category, subcategory or supplier

Once you have assign the new price list for the client, you should sync the device 

Main menu > More > Sync now 

Then you should do the following at

• Main Menu > Settings > Sales orders > Discount Structure > Type

Select Specific client (Custom $)

Remark all other clients will have the Price A by default.