I think for most of us here the appeal of booking a container ship route would be the isolation that hypothetically allows for uninterrupted programming plus the romance of the idea. On a cruise ship, you have to deal with personnel and other guests daily. Personnel might constantly be trying to engage you in social activities, you always have to tip everyone, and if you do bring a lot of computer stuff it might get stolen.

But that said, 120/day is not cheap. As a hacker getaway, you can book a hut by a fjord in Norway for far less than that...

And the hut by the fjord will have pretty good connectivity too.

Here's repositioning cruises, for less than $50: http://cruisesheet.com/?rt=0&max_cpd=80

You probably already know this, but as a heads-up to others browsing that site, quoted prices for cruise ships are per-person based on double occupancy, so you'll only get a rate as low as $50/day/person if you're traveling as a pair sharing a room. If you're traveling single, you pay anywhere from a 50-100% supplement. Picking a few of the ones from that site at random, it looks like most are charging the full double price if you want to book a room as a single, so ~$80-100/day. Add in the ~$10-15/day quasi-mandatory gratuities and you end up not saving much vs. the $120/day container ship, though certainly for a much different kind of trip.

The least costly line I know of is Pullmantur. Their repositioning cruises across the Atlantic are frequently under $50/day for a solo passenger.

US$37 / day at current exchange rates and including taxes and semi-obligatory gratuities: http://www.pullmantur.com.br/pt/cruzeiros/-/cruzeiros/posici...

US$39 / day: http://www.pullmantur.com.br/pt/cruzeiros/-/cruzeiros/transa...

Heads-up: English is not the primary language of most passengers, but from what I've read, the crew can accommodate it.

Norwegian also has some that are under $100/day including taxes and gratuities. The one below is $968.95 for 13 days ($75/day), assuming you take the promo where the cruise line pays for the gratuities.

http://www.ncl.com/cruises/STAR13DVRPDLMIATPA?itineraryCode=...

(click all the way through to the final pricing page - the first page isn't what you get charged)