Yours for £3,900...the WC that's really a throne

Think of it more as a throne than a lavatory.

Only then, perhaps, can the thought of spending almost £4,000 on the thing be justified. The American manufacturer Kohler has begun marketing its newly developed Numi, a lavatory costing $6,390 (£3,900). The company clearly feels there is a gap in the market for loos that do more than just flush, because for that sum buyers are treated to a heated seat, foot-warming hot air vents, a deodoriser, motion-activated seat and lid, illuminated side panels, a bidet and a bottom dryer.

Also included are a touch-screen computer panel and a built-in sound system with speakers playing either pre-programmed music or FM radio.

The company has not scrimped on its advertising budget either. Its website does everything possible to make the toilet look like a glamorous home accessory, depicting a stylish young couple posing with the loo, which is discreetly tucked into the corner of their modernist glass-walled Hollywood Hills penthouse. This is a lavatory, it suggests, good enough to deserve a place not just in the bathrooms of the rich and famous, but in their living rooms.

The Numi does have some competition. Even on eBay, customers can splash out on the Geberit AquaClean 8000plus Care Automatic, available for £2,699.99.

Although the Numi exceeds that figure by quite some distance, it remains a long way from being the most expensive lavatory in the world. That title belongs to the one produced by Hang Fung Gold Technology in Japan, which is made from 24-carat gold. Made at a time when gold was worth much less than today, its original value was $5m, but the spike in the metal's price means it is now worth approximately $37m.

The founder of Hang Fung, the Hong Kong jewellery entrepreneur Lam Sai-wing, originally said the toilet would be melted down when gold reached $1,000 an ounce. That occurred some time ago now – its price is currently $1,477 – but his affection for the glittering loo means that he can no longer contemplate destroying it.

"I don't care if gold hits $10,000 an ounce," Mr Lam said in 2008. "I'm not melting it down."

He held less of an attachment to the rest of the bathroom fittings, however – the golden sink that originally stood alongside the lavatory was sold off when the price of gold hit $800 an ounce.

The golden toilet's $37m tag dwarfs even the figure quoted for the convenience on board the International Space Station, which is able to recycle urine and turn it into drinking water but is worth a mere $19m. This was a considerable development from the previous system, which stored waste in tanks before launching them into space to burn up in the Earth's atmosphere.

Jim Lewis, Kohler's vice-president of marketing, believes that there is no match for the Numi. "It's truly an innovative product that makes a bold design statement," he said. "We envisioned a toilet that creates a category in a calibre of its own. Numi packs technology into a compact toilet and is controlled by an advanced and intuitive interface. It's an astounding example of modern industrial design where form and function go hand in hand."