Check the instructions for the channel if this feature is supported. If the instructions do not mention the option to add a multiplier please send us a support ticket (click on HELP in the top right in the channel page in the control panel) and we will see if we can add it.
[[Image:channel-manager-multiplier.png|450px|link=]]
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Note:
The prices will only be sent to the channels you have activated in the channel manger settings.