The Ace of Diamonds garden will be littered with precious stones supplied by some of Bond Street's most prestigious jewellers.
Domoney said: "I always endeavour to introduce something a little bit more entertaining and this is something really special. It's high-end and extreme but with a strong horticultural message. This garden will be worth more than the rest of the show put together - worth more than this year and last year combined even."
The urban garden is the second of four Domoney gardens designed for the airline BMI's Diamond Club, following on from last year's Ace of Spades garden.
It will feature plants with names from the world of jewellery, including Sedum 'Diamond Edge,' Campanula 'Blue Diamond' and Hosta 'Diamond Tiara'.
Diamond-shaped stepping stones will lead in to a diamond-shaped patio, giving a bird's eye view of a diamond necklace.
The garden will be produced in association with luxury jeweller David Morris and Domoney predicted that security will need to be equal to that for the royal visit.
RHS shows director Stephen Bennett told HW that Domoney would use a helicopter to deliver the precious stones to the site.
While the value of the garden exceeds anything in the show's history, the Eden Project garden remains the biggest ever shown.
Domoney designed three gardens at this year's Ideal Home Show in London, which attracted 250,000 visitors.