The minimum quantity is 100pcs/per order, but 200 pcs/per order will be better off for us preparing the raw materials.
Please correct if there are any mistakes. Thank you in advance.
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The slashes and the 'per's mean the same thing, so one of them is redundant:
'The minimum quantity is 100 pcs per order, but because of raw material preparation, 200 pcs/order would be better for us.'
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Thank you, MM.