Director Karen Craig said because a venue like the Bason wasn't usually used for events, regulations required a maximum of 100 people to be onsite.
"Obviously that's not financially viable," Craig said.
"Normally we average between 750 and 800 audience members in total over the four performances.
"We have to count in our cast and crew as well."
Craig said auditions were held online during this year's lockdown, and rehearsals began in September.
The decision to postpone was made before "the big bucks" began to be spent.
"This weekend we would have started painting all the sets.
"All the cast and crew have been engaged. Everybody was understanding and said 'It is what it is'."
At this stage, all members of the production were still on board for 2023, Craig said.
"I'm a little bit worried that if the boundaries do get opened, a lot of my cast and audience might disappear overseas.
"We'll deal with that if and when it comes, though."
The postponement meant there would be plays in both 2023 and 2024, Craig said.
"We usually do this every two years, so the lucky citizens of Whanganui will have two Shakespeares a year after each other."
The Merry Wives of Windsor will now take place in February, 2023.
