Some have said it is "grossly insensitive" but Simon Woolston says he is "taking the lid off funeral poverty."
Mr Woolston, who runs Heavenly Services in Hull, says the industry is a rip off with the bereaved routinely overcharged huge amounts.
He charges just £1,700 - half the national average - and says he still makes £600 net profit.
It comes as the Competition and Markets Authority investigate the £2bn funeral market to ensure people are not getting a bad deal.
The average funeral cost hit nearly £3,800 last year, before "extras" which the CMA said could add another £2,000 to the final bill.
Mr Woolston said: "I really want to make it clear to people that funerals are not as expensive as people are led to believe.
"All we have to pay out is £710 for cremation, £164 for doctors' fees and a coffin for £150 - other than that everything else is profit."
Over the weekend he had been hit by allegations on social media - including that his hearse was like something from the Addams Family - which he thinks stems from rivals who "are petrified of what we are going to do."
Mr Woolston said he paid £2,500 for the 40ft by 20ft poster. "I have another one going up in two weeks to apologise in case it caused any distress. I wanted to cause a controversy .
"It was aimed at getting people to speak about it. I don't want people to be worried when they pass away about finding the money."
Research carried out for the CMA suggests that people do not worry about the cost at the time as long as it fits with "ballpark" estimates.
However later "a small group of respondents questioned why funerals were so expensive and to what extent this cost was justified."
Many did not feel they could negotiate with the funeral director as it would make them feel and seem like a "cheapskate."
It concluded that consumers would benefit from independent advice on arranging funerals and raising awareness of variations in prices may be a way forward.