They do it for God - in particular Lord Venkateswara, a local incarnation of the Hindu deity Vishnu, whose white and gold temple soars next door to Tirumala's concrete shed ("The Place Of Surrendering Human Hair To Lord Venkateswara Swami"). Give a gift to Venkateswara, they believe, and he will allow you a wish; for the poor who make up most of the pilgrims, hair is all they have to give when they arrive.
And its loss is not all they endure. Coming from all over India from early dawn until after dusk, with the last 20 miles a vertiginous climb by bus up to Tirumala's scrubby plateau, the pilgrims must first shuffle through long wire cages designed to keep them in orderly lines for as much as 12 hours - a claustrophobic form of crowd control which allows neither a way out nor a chance to change the mind - before meeting the barbers. Children scream and beggars thrust their hands in through the wire; shortening this ordeal to a mere two or three hours requires a cash donation to the temple. Once shorn, the pilgrims are bundled forward again by those behind, finally catch a glimpse of a small carved figure of Venkate-swara, receive a free meal, and are pushed out of the temple.
The motivation for all this is simple: by repute a greater proportion of wishes are granted at the temple in Tirumala than at any other in India, thus making it one of the most visited pilgrimage sites in the country (and the world). The pilgrims have been coming for two centuries; for several more the temple has been massively enriched by gifts to Venkateswara. In 1513, Krishnadeva, the Raya King, gave pearls, a crown, a jewelled sword, and 20 plates of silver. The following year he won a string of battles and gave 30,000 gold coins. Thanks to such stories, the temple's income was 5bn rupees (pounds 100m) last year, making it one of India's richest. Most of this money goes back to the pilgrims, indirectly: cheap accommodation is provided for the poor; there is even a local university. A substantial town has grown up around the temple - which alone employs 6000 people, 600 of whom are barbers - including an airstrip for the richer pilgrim.
But what happens to the hair? Every day three tons of it are carefully swept into piles across the vast floor of the concrete shed, washed, bagged, weighed, and sent to nearby Madras. There it is dried in the sun and sorted according to quality, colour and length. Then, every three months, buyers from Europe and America and the Middle East arrive to bid for the best locks - white hair is worth the most (pounds 200 a kilo), for its easy-colouring properties; long black hair is in demand in Spain and China.
Once shipped, the hair is woven into wigs and hair-pieces, and the temple at Tirumala receives over pounds 1m every year in return. It's easy to suspect something exploitative, or degrading, in the whole process: in the long hot lines in the cages, in the heads cruelly bared like those of concentration camp prisoners, and in the sight of Third World religious faith - and body parts - helping cover the scalps of richer people in richer countries. But once they leave Tirumala, the pilgrims' shaven heads carry prestige, and that pounds 1m goes back to the temple's university and local craft workshops. Who knows how many wishes are being granted as a result? !