Mahons is by far the biggest company dealing in fairground amusements but Mr O'Neill said the show committee "has got someone else to do what they [Mahons] do, on a similar scale."
"Some of Mahons' rides are pretty antiquated, they didn't always want to bring their best rides to our show," he said.
Mr O'Neill said the decision to drop Mahons was not purely financial.
Masterton A&P Association has no debts, cash reserves are good and more than $1.5 million had been spent in the past four or five years doing up Solway Showgrounds, he said.
Last year a family pass cost $25 and Mr O'Neill said there had been complaints that by having to pay for rides on top of that a family could easily spend $150.
The February show will be the 128th and Mr O'Neill said he was confident it would prove to be "a fun day out for everyone".
" It's quite exciting really, I think people will flock in."
A press release giving further details would soon be issued.
Mr Mahon, who was packing up at Clareville after a successful three-day Carterton show, said although he was disappointed, he realised the committee had the right to make decisions.
He said he had got a letter and had a telephone conversation with Mr O'Neill but would have expected wider consultation before a decision of that magnitude was made.
Mr Mahon said it was his understanding the family pass would cost $50.
He said the show might manage to get a few small entertainment attractions "such as bouncy castles and things for small kids."
"Those things won't get the teenagers in," he said.
Mr Mahon said he believed Masterton's show had been "weak for quite a while".
If the decision came down to money he found it strange the Carterton show "only 10 kilometres down the road" was working well with the same rides and prices offered to Masterton.
Mahons founder, Roy Mahon, set up the company while remaining in work as a miner in winter months and running the amusements business in the warmer months.
Later his son, Bill Mahon, took over but was killed 10 years ago with the business passing to his brother, John.
Bill Mahon's son Paul has been with the firm for a decade and John Mahon's son, Christopher, has also signed up.