SEOUL, March 24 (Reuters) - For Maria Herrera, a utility

employee from Vancouver, the trade-off to watch a performance by

Kpop supergroup BTS on Saturday in Seoul was simple: Weeks of

extra shifts at her job and roughly 5,000 Canadian dollars

($3,644) for a week in Seoul.

The 58-year-old was willing to make the trip without having

secured concert tickets as she and her two daughters were

looking forward to soaking up the pre-concert atmosphere and

pampering themselves afterwards with Botox, haircuts and some

Korean barbecue.

Maria and her daughters are part of a global wave that

analysts at NH Investment & Securities say could generate a

windfall of 8 trillion won ($5.32 billion) across the 44 cities

that will host BTS' world tour - a phenomenon that they have

dubbed "BTSnomics."

"We don't do our hair in Canada," Maria said, emerging from

a crowd of fellow ticketless "BTS ARMY" members waiting in the

crisp air in downtown Seoul's Gwanghwamun Square 10 hours before

the show. She added that because they were in Korea, they would

treat themselves.

"For myself Botox, facials, Potenza and all that stuff,"

Herrera said. "And then we do our hair care here, like we do

haircuts, we do our color and all that." She added that her crew

also planned to travel to Toronto for another BTS concert.

While turnout for Saturday's show fell short of the 260,000

that was projected, the real financial power lies with fans who

are eager to spend on services and merchandise.

"Performances by artists with a global fandom like BTS do

not end with ticket sales, but drive tourism consumption

throughout the entire city," said Lee Hwa-jeong, a researcher at

NH Investment & Securities, adding that the 8-trillion-won

estimate included direct revenue and secondary consumer

spending.

Past record-setting world tours by pop superstar Taylor

Swift and British rock band Coldplay have also been credited for

helping local economies, though economists have generally been

skeptical about concerts or big sporting events providing more

than a small boost to a country's economy.

BTS' world tour will kick off on April 9 in the South Korean

city of Goyang and will make stops in Las Vegas, Los Angeles,

London, Paris, Tokyo, Singapore and other major destinations.

Analysts have said ticket sales could rise as high as 2.7

trillion won because BTS plans to use a centralised stage for

the shows, which would have no obstructed views and could

increase audience capacity.

South Korea is already reaping the benefits from BTS'

Saturday reunion. The band had been on a hiatus of more than

three years because some members needed to fulfill their

mandatory military service.

In the week leading up to the free concert, sales of BTS

merchandise - from glow sticks to blankets to dolls - rose 430%

from a week earlier at Shinsegae Duty Free's headquarters in

Myeongdong.

At the Lotte Department Store in central Myeongdong, revenue

for the weekend jumped 30% from a year earlier; for Shinsegae,

it jumped 48%.

The number of inbound tourists for the first 18 days of

March was up 32.7% from a month earlier, data from the Ministry

of Justice showed, pushing up hotel rates in downtown Seoul.

Hotel rates in Busan, where BTS will perform in June, have

surged as much as seven times at some venues.

Stephanie Gonzalez, another ticketless BTS fan from Mexico,

said she flew in two weeks ahead of the concert to experience

"ARMY life to the fullest."

"I've been visiting pilgrimage sites like the old BigHit

office and Hakdong Park," the 25-year-old said, referring to

sites famous among fans because BTS members had been seen there

in the past.

"I wanted to experience every place BTS has been to make the

most of this trip," she said, adding that she spent about 90,000

Mexican pesos ($5,028) altogether even after staying at a

no-frills hostel.

And in addition to the tourism boom, local fans are getting

in on the action.

Huirin, a Seoul resident in her 50s, says she took a cab to

Gwanghwamun on Saturday after getting her hair done to "save

some energy on commuting."

"Are you kidding me? No woman - I mean, no ARMY - would go

to a BTS event without dressing up," she said as she proudly

showed off the BTS merchandise in her bag and the purple shirt

that she wore beneath a black outer layer.

(Additional reporting by Minwoo Park, Jungmin Ryu; Editing by

Brenda Goh and Thomas Derpinghaus)