What price street art? (Quite high, actually)

Marc Jacobs's tweet, showing off the new t-shirt and its ridiculous price tag

One of the obvious problems with street art is that while it might try to highlight social ills, it can end up selling for many thousands of pounds to the elite that it supposedly rails against.

Take the French graffiti star Kidult, who last week sprayed the word "ART" in huge letters over fashion designer Marc Jacobs' boutique in New York. Shortly afterwards Jacobs' team took an Instagram picture of it and posted it to Twitter with the words "Art by Art Jacobs" (a play on the designer's line, Marc by Marc Jacobs). They have now produced a T-shirt with the picture and the phrase – the price, a mere $689.

Meanwhile, the UK's Banksy is believed to have struck again with a new work reflecting the Queen's Jubilee. On a wall in north London, it features an Asian boy working at a sewing machine to create Union Flag bunting. It's surely only a matter of time before someone chips it off and attempts to sell it...