why we not suggest sample by sea

We have been back and forth with a USA customer recently regarding one pcs of electric scooter SAMPLE unit that the customer believe our air shipping cost to his door is very expensive! And he insist will purchase from another vendor with 60% cheaper shipping cost by sea.I tell him by sea it is cheaper from our side but once it reach his destination port,the local port charge is at least $300~400,he doesn't believe our suggestion to him.

So lets make it clear how much it is exactly cost for SAMPLE by air and by sea :

AIR express by ups for one single pcs scooter to USA consignee's door is $400 ( UPS charged weight according to package dimension volume weight that is 33kg),plus Dangerous Goods handling fee,over sized package fee and delivery cost to consignee door directly without any hidden or extra cost.Total duration delivery time is 20days.

SEA shipping by boat for one single pcs scooter to USA main port is just $90,after 1 week export customs clearance, 35days boat shipping,total takes 42days reach consignee's main port,then consignee will need to prepare import customs clearance paper and process import duty and delivery from his port to his door by truck,this will take another 2 weeks,so total 42days+14days=56days reach consignee's door.

Well,lets see how much destination port and truck delivery cost:

destination port fee+import customs clearance +import duty =$350

truck delivery to door =$85

final cost :$90+$350+$85=$525

So air delivery cost $400,and just 20days reach consignee's door directly,sea delivery cost $525 and take as long as 56days reach consignee's door finally,which way is best cost effective? Of corse by air which is more cheaper,time saving and more simple job!