Migrants attempting to reach the UK are paying smuggling gangs as much as £13,500 to arrange their journey, the National Crime Agency (NCA) has revealed.
Some of those intent on coming to Britain are quoted five-figure sums to make the trip by air, while others are even believed to have spent as much as £12,000 to travel from France in inflatable boats.
It also emerged that criminal networks are suspected to have begun targeting quieter ports on the east and south coasts in addition to the key hotspot at Kent.
The NCA - the UK's equivalent to the FBI - is running the largest dedicated operation against organised immigration crime in Europe.
Officers said the cost of journeys varies hugely depending on the service being sought from the gang.
Factors that affect the price include whether the migrant wants a staged or "end to end" trip, how much they can afford and the level of risk perceived by smugglers.
Tom Dowdall, deputy director of the NCA's border policing command, set out examples of the sums for those attempting to come to the UK.
Someone wishing to travel from Iraq to the UK could pay just under £4,000 to go over land through Turkey and Europe, while the price jumps to more than £13,500 for a journey by air.
Referring to the more expensive example, Mr Dowdall said: "That's someone who has been able to access a good quality travel document in the first instance to be able to cross borders and to be able to fool airlines as well."
Asked how frequent such activity is, he said: "There is a regularity to that."
The cost and sophistication of efforts to smuggle migrants into Britain from France also varies considerably.
Prices can range from as little as just over £100 for a single, basic attempt to more than £6,000 for a journey in a "high-quality concealment".
Intelligence even suggests that some migrants have paid up to £12,000 for transport from Dunkirk to the UK in Rigid Hulled Inflatable Boats.
The criminal networks are seen as adaptable, quickly changing their methods in response to law enforcement action or increased security.
Investigators suspect that, as well as the main Channel crossing between Calais and Kent, criminals may be using less busy ports within the UK.
"We've seen on the east coast evidence from Tilbury and Purfleet, up as far as Hull and Immingham. And on the south coast from Newhaven to Portsmouth," Mr Dowdall said.
The NCA provided examples of recently detected "concealments".
One migrant found in a tanker at Dartford Crossing had travelled from Iran to Calais via Turkey, Hungary, Bulgaria, Greece, Austria, Switzerland and, once in France, Paris and Lille.
He had paid around 4,000 US dollars (£2,800 at current rates) to various "agents", with the journey to the UK costing an additional 1,000 euro (£800).
In another episode, six men found on a freight train near Folkestone reported that they had paid 500 euro (£399) to get on at Calais, where they were sealed in containers.
The NCA's 90-officer taskforce - codenamed Project Invigor - has up to 60 open lines of enquiry into organised crime gangs at any one time.
Groups involved are often formed along national or community lines, including those from the Middle East, China and various Eastern European countries. British-based groups are often comprised of naturalised UK citizens.
Smugglers find their "customers" through word of mouth recommendations, at transit hubs and through advertising on social media, the NCA said.