Long past their prime, the two ships picked up by the Italian navy may have been worth just $150,000 (€126,000) each in scrap, and likely changed hands in an underworld out of reach of the authorities, according to shipping experts.
Neither Ezadeen, the 48-year-old livestock carrier found with 360 desperate migrants on board, nor the 37-year-old cargo ship Blue Sky M, carrying 768 people, had up-to-date certificates of seaworthiness demanded of normal commercial ships.
"For these ships, there is no value except scrap," said Simon Ward, director of Ursa Shipbrokers in Piraeus, Greece.
But neither would attract more than $250,000 each in scrapyards in Turkey, he told AFP, and with a potential cost of transport reaching up to $100,000, unscrupulous owners might look favourably on a cash buyer.
"If you can get someone to take the ship for peanuts and put migrants on board then you can see the attraction of it," said a shipbroker in London, who asked to remain anonymous.
"It's like buying a second-hand car - it's that easy."
The potential profits are huge. Italian officials said passengers on Ezadeen paid between $4,000 and $8,000 to cross the Mediterranean, netting the smugglers between $1.44 million and $2.88 million.
'Plenty more out there'
While it remains unclear how the ships were commandeered by the smugglers, there is no suggestion they were stolen.
The International Maritime Bureau has no record of their theft and automatic trackers on both ships were operational when they were taken over by the Italian navy.
"It's entirely legal to sell a second-hand ship anywhere in the world," said David Olsen, an editor with London-based maritime newspaper Lloyds List.
"It has been known for cargo ships to turn up on eBay. Certainly there are websites that will give you bargain basement ships."
He added: "I can see people meeting over a beer and agreeing a price that is more than the scrap, to take it off their hands."
Many reputable brokers deal in second-hand ships. But buying creaking vessels with dodgy paperwork is far removed from the normal commercial trade.
"This is in a market outside the main trading markets. The reputable dealerships don't deal in this kind of area for fear of being tarnished," added the London broker.
"There are ships that trade in the eastern Mediterranean around Turkey, around Syria, Lebanon, north Africa, which aren't under the same kind of scrutiny or regulation.
"There will be plenty more out there."
'Bought as part of scrap deal'
Ezadeen was last inspected by local authorities in June 2014 in Lebanon and Blue Sky M was inspected in Romania in April 2014, in the countries where their respective managers are based.
Neither appeared to have a certificate of classification from an internationally recognised body, which essentially acts as a marker of seaworthiness, Ward said.
He suggested Ezadeen "may have been bought as part of a scrap deal, or been sold by the original owners thinking it was going to go for scrap and somebody stepped in between and took her over".
The construction, equipping and crewing of ships are subject to strict regulations developed by the International Maritime Organization, which comprises about 170 countries.
These rules are enforced by countries where the ships are flagged and also individual ports - but some authorities are less vigilant than others.
The Blue Sky M was flagged in Moldova and Ezadeen in Sierra Leone, both countries known to be less strict than, for example, European Union countries.
Ships flagged in Moldova comprise seven of the 20 vessels currently banned from the Paris MOU, a group of 27 maritime administrations in Europe and North America.