Anyone who argues the British Royals cost too much hasn't asked the royal retailers. 

U.K. merchandisers are anticipating making millions of pounds off the yet-to-be-born royal baby — and even its bottom. 

The pending birth of Prince William and Kate's first child has spawned everything from purple nappies emblazoned with a golden crown to "Born to Reign" sleepwear and an entire regal nursery suite in a five-star London hotel.

ii-croft-220-cp-04421828

Lucinda Croft, managing director of Dragons of Walton Street, shows a luxury baby changing unit at a nursery suite her company designed in the Grosvernor hotel. (Lefteris Pitarakis/Associated Press)

"People are mad about the Duke and Duchess of Cambridge's baby. The love for that baby is just so moving and overwhelming," says Lucinda Croft, a bespoke nursery designer at Dragons of Walton Street. 

Croft's mother once sold baby furniture to Diana, Princess of Wales, for baby William. Thirty-one years later, Croft's company has designed a "Dream Suite" at the Grosvenor Hotel to coincide with the royal arrival due any day now. 

It boasts a corniced crib with handpainted Buckingham Palace guards and a child's table and chairs decorated with London landmarks: Big Ben and the red double-decker bus.

There's a change table, a bottle warmer and a chaise longue created for nursing. It all comes at a royal price, too: more than $3,350 a night.  

At the opposite end of the baby bonanza is a return of the paper "sick bags" with their slogan "Well Brought Up."

The gag bags first surfaced during the royal wedding of William and Kate in 2011. They were such a hit that Lydia Leith updated her idea for this summer. 

'Slightly shocking'

"Something different, slightly shocking that makes people look twice and think hang on a minute — a sick bag? What? I think that's a good way of getting people to remember your product," says Leith.

Even Prince Charles, the future granddaddy, is selling Union Jack-themed baby booties from the shop at his Highgrove country estate. Part of the profits goes to charity.

A Buckingham Palace spokesman says baby merchandise was on offer long before this pregnancy was announced.

It's no surprise that the Duchess of Cambridge's bump is creating as much of a stir as Kate herself. She is a walking billboard and a few of her maternity dresses and coats sold out within hours of her being photographed wearing them.

A London shop where she bought a Moses basket for the baby is now a tourist destination. 

"The impact has been enormous," says Izabela Minkiewicz, owner of Blue Almonds shop. 

"I think anything she associates with, she relates to, will become the 'in' product at the moment. The choices she's making even related to the type of birth, or the services she's receiving will set the trends for at least the next few seasons." 

The Centre for Retail Research in Nottingham, England, estimates the birth will spawn $380 million in retail sales over nine summer weeks. That includes toys, DVDs and parties with an estimated three million bottles of sparkling wine and champagne uncorked to toast the newborn. 

Just projections

Suppliers of prams and cribs are expected to exploit the interest in the royal baby to sell more products abroad, especially in the United States where this generation of British royals are celebrities and in Commonwealth countries such as Canada. 

But retail projections are just that — projections — until the baby is born and the high street assesses the effect of a Prince or Princess of Cambridge. 

During the London Olympics in 2012, some sellers were disappointed with anemic demand, leaving them with piles of unwanted Olympic merchandise. 

The baby buzz is just beginning, with many Brits still holding fast to the belief it is bad luck or just plain improper to celebrate the baby in advance. 

"We need to know that everything is good because at the end of the day having a baby is still a risky activity," says Pauline Maclaran, a professor of marketing at University of London. 

"I think everybody wants to know that it's a healthy boy or girl and that it's all gone well for Kate."

Maclaran believes the longer-term effects of the new royal baby and any possible siblings will outstrip any short-term bump in sales. 

"It's likely to influence fashion and the baby merchandise market over the next 12 to 15 years," she says. 

Back at the hotel suite, Croft is reflecting on the days just before Prince William was born. 

"Diana walked quietly into our shop and talked to my mother. It wasn't the fever pitch that it feels now, you know, it feels like just sort of this frenzy."