NEW YORK (MainStreet) — You can expect to pay a pretty penny for holiday gifts come Black Friday. And on Cyber Monday too.

BMO Harris Bank says shows that on average Americans will spend $418 on Black Friday and $373 on Cyber Monday (which arrives Dec. 1). Forty-four percent of U.S. adults say they will spend more on holiday gifts on Black Friday than they did last year, and 40% say they will spend more on Cyber Monday. 

The optimism stems from a generally positive outlook among Americans on the economy, BMO Harris says.

"The U.S. holiday shopping season is expected to be moderately better this year due to stronger job growth, lower unemployment, improved confidence, record-high equity markets and lower gasoline prices," says Sal Guatieri, senior economist at BMO Capital Markets. "The only thing holding back sales is sluggish wage gains, though that is expected to change next year. Price competition should remain fierce this season as a result."

Another key factor is energy prices. Americans are finding a bit more cash in their pockets as the price of oil declines, leading to lower costs for filling the tank and for heating the home. Right now, the price of a barrel of crude oil is $75, and the cost of a gallon of gasoline is below $3 for the first time since 2010.

Consumers feel so good about the economy that 76% of them will be shopping for themselves on Black Friday (and 70% on Cyber Monday), BMO Harris says. And 55% say they have a holiday shopping budget but will exceed it, given their optimistic outlook on the economy. That isn't exactly a good idea.

"The week around Thanksgiving can be an expensive one, with travel and entertaining costs adding up in addition to sale shopping on Black Friday and Cyber Monday," says Alex Dousmanis-Curtis, director of retail banking at BMO Harris. "The best way to avoid overspending and taking on debt during this time is to build a detailed spending plan that accounts for all costs — from airfare to gifts — that will be incurred."

Another tip from BMO Harris: Plan in advance how you'll pay for holiday spending (55% of those surveyed say they will use a credit card). "Planning your payment method in advance can help with staying on track with expenses, as you're making the decision in advance and may be less tempted to make impulsive purchases that aren't within your budget," Dousmanis-Curtis says." If you do use a credit card, "earning rewards are an added benefit of using a credit card during the holidays." 

— By Brian O'Connell for MainStreet