Since 2005, all the couriers (TNT/DHL/UPS/FedEx) have stopped taking the fresh products like fresh truffles. Since then, the ONLY way to send the samples is by air freight like for the normal quantity shipments. By air freight, please note the following costs you may not 
be aware of:

1) For every shipment by air freight, no matter how big or small it is,  there is USD 75$ for export customs clearance and CCIB inspection cost.
2) For every shipment by air freight, no matter how big or small it is,  there is USD 10$ cost for Form A (certificate of origin).
3) The air freight rate:
below 10 kgs: USD 120$ which is the minimum freight cost charged by the air carrier;
11-45 kgs: USD 13$/kg
more than 45 kgs: USD 4.6$/kg which is the rate for the most of the main airport destinations in the world.
4) The air shipment is only air-freighted to the airports. As the consignee, you'll have to go to the airport to clear the goods and pick them up and the costs for this is not inexpensive.

Below are the costs for the sample ordering of 2 kgs, 5 kgs, 10 kgs, 20 kgs, and 40 kgs:

- 2 kgs of small size USD 33$/kg 

Product cost: 33x2=66$
Shipping cost: 120$
Export customs clearance and CCIP inspection: 75$
Form A: 10$
Total cost: 66+120+75+10=USD 271$
CNF unit cost: 271/2=USD 135.5$/kg

- 5 kgs of small size USD 33$/kg

Product cost: 33x5=165$
Shipping cost: 120$
Export customs clearance and CCIP inspection: 75$
Form A: 10$
Total cost: 165+120+75+10=USD 370$
CNF unit cost: 370/5=USD 74$/kg

- 10 kgs of small size USD 33$/kg

Product cost: 33x10=330$
Shipping cost: 120$
Export customs clearance and CCIP inspection: 75$
Form A: 10$
Total cost: 330+120+75+10=USD 535$
CNF unit cost: 535/10=USD 53.5$/kg

- 20 kgs of small size USD 15$/kg

Product cost: 33x20=660
Shipping cost: the gross weight including the outside packing is 23.32 kgs, the air freight rate is 13$/kg. The shipping cost is: 23.32x13=303$
Export customs clearance and CCIP inspection: 75$
Form A: 10$
Total cost: 660+303+75+10=USD 1048$
CNF unit cost: 1048/20=USD 52.4$/kg

- 40 kgs of small size USD 33$/kg

40 kgs already meets the minimum order quantity. For the quantity order, there is no more export customs clearance and CCIB inspection cost.

Product cost: 40x33=1320$
Shipping cost: the gross weight including the outside packing is 46.64 kgs, the air freight rate is 4.6$/kg. The shipping cost is:46.64x4.6=215$
Form A: 10$
Total cost: 1320+215+10=USD 1545$
CNF unit cost: 1545/40=USD 38.635$/kg

So, please try to make the samples order as big as possible. 

Please note that CNF cost does NOT include the costs at your end, such as customs clearance, over-land transportation, etc..