the are many ways to cross the sea :

1) by airplane : from Buenos Aires: TRUST CARGO INTERNATIONAL, 1100 usd for one motorbike

2) with container on the boat

We went with MSC , company in Anvers (BEL) ho works with Grimaldi.  We had bad service en ending paying more than was agreed...  We had a lot of problems getting the bikes out ( no problem with paper or douane but with the company ho do al the things to get the bikes out ) We lost 12 DAYS !
We met other people ho had the same experience with GRIMALDI and paid more than normal, lost more days than we, ect....
we paid: 850 euro transport and 1017 euro for paperservice in BA, price per bike - one way !

  in a box

We meth 2 polish guy's ho did the transfer with ECU Logistics . They paid half off what we paid en could leave the harbor after 2 day's! This company work all-in, so no surprises. 
We made also contact with this company to know the price for going back and it was 1780 euro for the  2 bikes, all-in !
This is the contact person in Buenos Aires ARG:
Mariela GLUSTEIN, AV Belgrano 355, 12the floor Buenos Aires
email: mglustein@ecuarg.eculine.net
This company has many off in al sur amerika, so look on their web ;
www.eculine.net

cost: 900 euro per bike, all-in, one way


3) with a Roro schip :

WE met 2 Koppel’s from Germany ho took a RORO ship and told us they where very happy with this service.
You go along with the boot, 4 weeks, all-inc en you stop many times in big harbors in Africa, Europe, sur-amerika.  The bikes a secure and when you come to BA, you do the paperwork with EMBA yourself and ride the same day out of the boot!

cost :  300 euro per bike and 1200 euro pp (3xday Italian food ) one way

- if you enter BA by boot you need 1 bill of Loading for each bike !

 - Temporal tourist import : the maximum time your bike can stay in the country

  ARG: 8 m

  CHI: 3 m

  BOL: 3 m

  URU : 12 m (ex if you take the boot from BA, you get 90 days )

 - a carnet de passage : is not needed for the countries we did, the never ask us the carnet on the border but it can be quicker than the ordinary paperwork.  Next time we will take the carnet with us and wil see of it made a difference.

 - assurance: must have and was ask sometimes on the border or by police control in Argentina. We went to Federation Patronal seguros in Buenos Aires and paid for insur. for ARG en CHI . This company has offices in the Mercosur landen (BR, PAR, URU, CHI, ARG, BOL) This is very handy because our insur. was accepted in all this countries !

 - always original paper of motorcycle with the proof your are the owner

 - declaration of value : is needed on the border sometimes.

 - selling your bike is not allowed but there is always a way if you ask about it....

 - renting bikes : lots of companies offer renting ( we have 3 good addresses ). With these bikes you can cross the border with Chile.  For long term they offer to sell the bike to you and later buy it from you again.... but you cannot leave the border of Argentina...

- we don't have info how to buy a bike in outer countries but we have contact in URU and we can ask