Proof of any sale of any farm product which is made by a commission merchant for less than the current market price to any person with whom he has any financial connection, directly or indirectly as owner of its corporate stock, as copartner, or otherwise, or any sale out of which such commission merchant receives, directly or indirectly, any portion of the purchase price, except the commission which is named in the licensee’s application or in a specific contract with the consignor, establishes a rebuttable presumption of fraud within the meaning of this chapter. This presumption is a presumption affecting the burden of proof.