For years the Denny's 'Grand Slam' breakfast was $2.99. Of course the minimum wage was $3.35 per hour and eggs were 89 cents per dozen. Utility rates were probably half or less what are charged today, so keeping those lights on and grills going 24/7 was a little less expensive.
Today, if you want the equivalent of the old Denny's 'Grand Slam' (2 pancakes, 2 eggs, 2 bacon, 2 sausages) you may get a little change out of your $20 bill.
Most of the 1980s my job required several days on the road each week, and frequently a week at a time every month or two. I planned $100 per day for expenses to cover motel, gas, meals and that was usually pretty close. Last week I spent 5 days on the road and spent about $1500 living pretty modestly. State fiscal rules allowed a maximum reimbursement of $34 per day for lodging, $5 breakfast, $6 lunch, $10 supper, and a receipt was needed to claim parking, tolls, etc.
In restaurants the tips we left were usually pocket change, not folding money.
Of course, back in the 1960s Motel 6 was actually $6 per night. Super 8 charged $8 but every room had a TV (hence the names for those chains). By the 1980s I could usually find a motel room for under $30, unless I had to work a case in Aspen, Breckinridge or Vail during ski season.