"If the world was square we wouldn't have this issue; but it's not fair and it's not square.
"The Government doesn't fully subsidise primary care and if you did a phone around of all the urgent care facilities in New Zealand you would find their fees are either much greater than ours or sit around the same.
"In an ideal world we wouldn't charge - but we're not fully subsidised so we have to charge."
MacDonald was sympathetic to those who would be hit most with the price hike.
"We recognise that any cost for some of our patients is quite a difficult issue and we're very sympathetic.
"But we don't get a Government handout if we don't break even or if we run at a loss and go broke ... no one is going to bail us out."
She said WAM had record numbers over the past year and it was time clients changed their attitude towards the clinic's purpose.
"We're about to hit 30,000 presentations for this past year. We've never achieved that volume of patients before."
A $10 fee for children to be seen at WAM between 8am and 5pm on weekdays was introduced last year.
MacDonald said that caused a big stir at the time but led to some behaviour change.
"We've seen a real turnaround of it shaping different behaviour - so people then organised themselves to go to general practice to get their kids seen."
Whanganui Regional Health Network business manager Teresa Hague said it was important WAM's prices didn't undercut general practices.
"WAM does not want to be the preferred provider of primary health care services for people in Whanganui.
"The best primary health care services for our population are provided in general practice where the patients and their families are known by the clinicians. WAM on the other hand is positioned to deliver urgent care services," Hague said.
MacDonald reiterated that.
"But some people choose to go to WAM because it's either convenient or they consider it an emergency.
"If people are worried about paying WAM fees and their general practice is open then they need to be assertive about getting an appointment and getting seen at their GP because they're the ones that get the funding. We don't."