427. The following are contributions:
(1) any gift of money to a party or to a candidate;
(2) any service rendered or goods furnished to a party or to a candidate free of charge and for political purposes;
(3) any money, goods or services furnished by the candidate himself in view of his election, except a sum of money used for the payment of an expense referred to in section 454.
Where goods or services are furnished for political purposes to a party or candidate at a price lower than their value, the difference constitutes a contribution.
For the purposes of this section, goods or services furnished by a trader dealing in similar goods or services shall be assessed at the lowest price at which he offers his goods or services to the public at the time they are furnished to the party or candidate; goods or services furnished by a person other than a trader dealing in similar goods or services shall be assessed at the lowest retail price at which they are offered to the public in the ordinary course of business, according to the market conditions prevailing in the area at the time they are furnished to the party or candidate.