From the Official Guidebook (p. 151-152):

After watching the mighty waters of the Columbia being manipulated to man’s use, you must be thirsty. You’ll find public drinking fountains as plentiful as kids at the midway. But if you want to part with 20 to 40 cents, you can buy anything from a hot drink to an ice cold beer. 

In the Hunger department the prime requisite is a steel-like determination. All those sights and smells can wreak havoc to willpower. The average dish price from food stands is projected to be 70 cents. Or you may decide to brown bag it and eat your lunch at a tree-shaded grotto overlooking the south channel of the white-foamed Spokane River.

For dinner you may partake of anything from Belgian waffles to pizza… French onion soup (the real thing) to Philippine Camaron Rebosado (jumbo prawns stuffed with beef and pork). Curry from India, tempura from Japan or authentic fried rice from China (there is a difference), or the ubiquitous hamburger. It’s all there for consumption at prices ranging from that 70 cents to $3 for a formal, sit-down dinner.

If you haven’t eaten dinner yet, you’ve spent $3.80 so far (assuming you had beer instead of coffee). You can buy a souvenir for the folks back home (an oyster guaranteed to have a pearl) or a monkey pod carved salad bowl. Depending on which of the 184 days you are attending Expo, your splurge could be the Los Angeles Philharmonic for $5; Championship Skaters of the Soviet Union for $2; Helen Reddy at $3.25; “Don Juan in Hell” with Myran Loy, Ricardo Montalban, Edward Mulhare and Werner Klemperer for $3.50. 

Assuming you saw Helen Reddy for $3.25 and spent $2 for dinner, your wallet is minus $9.05. If you’re still not ready to call it a night and are feeling flush, over 350,000 square feet of amusement park beckons.