It was a revelation for Vanessa Ali when she took her boyfriend Kevin Tomas food shopping for the first time. He took one look at the prices and told her to put everything back.

"I don't think he realized how much food costs," said Ali, 29, a communications manager at BMO Financial Corp [BMOHF.UL] in Toronto.

She went back the next day and filled her cart with the exact same stuff - this time without Kevin.

In some households, the cost of the daily grocery bill or the restaurant tab may be minor footnotes. But often, experts say, food bills can be a sore point.

"Research shows that the brain perceives food and money as almost the same thing," says Deborah Price, founder of the Novato, California-based Money Coaching Institute and author of "The Heart of Money."

Usually, arguments over food bills involve more than the mere cost of milk, bread or organic kale.

"They are often about underlying issues, like security, or health, or deep emotional fears," Price says.

DOLLARS AND SENSE

To be sure, in a challenging economic era for the middle class, food can make up a significant part of a household budget.

The cost of dining out could well be a key candidate for budget discussions. However, the average household bill for that was $2,625 over the course of 2013, according to the Consumer Expenditure Survey from the Bureau of Labor Statistics. That's just 5 percent of total expenses - and nothing close to what people spend to fill up their fridges.

Meanwhile, for daily groceries - the entree of many a budget altercation - an urban family of four might spend $800 a month, or $1,000 if they have a penchant for the organic, Price estimates. Indeed, the average American household dropped almost 8 percent of total expenses on food at home, according to BLS data.

"That's a lot of money," Price says.

One study by New York City-based consultancy AlixPartners found that health-conscious "superusers" - about 26 percent of the population, and usually female - spent four times as much of their monthly health-and-wellness budget on fresh fruit and vegetables, compared to the average shopper.

And another study in the British Medical Journal estimated that eating healthily costs an average of $550 a year more than the alternative.

With a preponderance of diets demanding specialty ingredients - from vegan to all-organic to gluten-free to paleo - the cost of meals can add up.

"Sometimes couples have very different views about food," says Richard Vitaro, a director at AlixPartners and the study's co-author. "Maybe one person values it a bit more, and wants a higher-end product, while the other is more value-focused."

"There can also be changes during the relationship," Vitaro notes. "Maybe they start off with similar views, but then one partner goes on a health kick," he says.

DEEP-SEATED ISSUES

Price recalls one client whose Depression-era father would only buy price-cut food in dented cans and seek big discounts on near-putrid meat.

That client later became "over-focused" on food, aiming only for the best and freshest produce to compensate for those early, disturbing memories, paying a ton of money in the process.

A palatable solution for conflicts over food purchases could be a negotiated compromise. Instead of splurging $100 a month on organic honey alone, as another of Price's clients used to do, try to find some reasonable middle ground.

If your projected monthly family food budget is $800 and your organic-obsessed spouse's is $1,000, at least try to split the difference and come in at $900.

Advance planning and price comparisons may help. Buy staples at big-box discounters like Costco or Target, says Price. That will help chop your overall bill and give you wiggle room to afford fresh produce on an as-needed basis.

As for Vanessa Ali, her household expenditure on groceries is about $550 a month - including a healthy array of fresh fruits, fish and veggies - and excluding eating out about three times a week.

She admits her partner "may have a little bit of a point" about their ample food budget, but that hasn't stopped them bickering over bills.

"Oh my God, I don't even want to think about the numbers," she says. "I think I'm in denial."