The colourful celebrations normally span three to five days and attract 500 to 1,000 guests, pushing the cost for the hard-hit lower middle class to between 300,000 and one million rupees (3,600-12,000 dollars).
"It has become too expensive. Everything is expensive. Even a simple wedding could break the back of poor people like me," said Mohammad Aslam, 62, a retired government employee.
Aslam spent most of his pension on marrying off his elder daughter, forcing him to borrow 200,000 rupees to help fund his second daughter's wedding.
A large part of the spending goes on gold jewellery, as in other South Asian countries, but sales are down partly because of rising global gold prices, businessmen say.
Gold surged to a new record high of 1,095.80 dollars an ounce during international trading on November 4.
"A year ago there was a demand for 7,700 ounces of gold daily, only for making jewellery in Pakistan. But now it has substantially decreased," said Haroon Chand, a leading member of the country's jewellers' association.
Imports of gold through Dubai, which was Pakistan's main source of the metal, have fallen significantly, he said.
"Affluent and middle class people have halved their spending on jewellery."
Poor families usually have their old jewellery redesigned for the weddings of their children, he noted.
"I tried to skip some of our customs to reduce the cost of my son's marriage, but I couldn't because of family pressure," Ahmed Ali, a car mechanic, told AFP at his son's wedding in Karachi's Ranchore Lane.
"My wife wanted all that because he's her only son. My son is also a mechanic and we have decided to repay the loans jointly as soon as possible."
Pakistani families spend lavishly on gifts for the happy couple, food for guests at wedding events that drag on for days, or on a sumptuous dinner offered by the groom's family at a wedding hall.
"What disturbs me most is that my daughters have also reached adulthood and their marriages will only be possible by taking more loans," said Ali.
"Like me, the bride's family has also taken loans for the marriage. We are all prisoners of our customs," he added.
Chand blamed deteriorating law and order, increased taxes on gold imports, the weakening purchasing power of ordinary people and higher global gold prices for dealing the business "a big blow".
Falling gold sales have seen people like Mohammad Akram, 33, laid off.
Until recently he worked as an artisan at a leading jewellery shop in an upscale neighbourhood of the teeming financial capital Karachi, a city of 14 million people that sprawls by the Arabian Sea.
"I am a skilled worker but am forced to ply a rickshaw to support my children," Akram said.
But Nauman Ahmed says business has boomed at his costume jewellery shop during this year's wedding season, between the Muslim feasts of Eid al-Fitr and Eid al-Adha, because its fashionable designs are "cheap and affordable".
Instead of gold, people are increasingly opting to buy silver and costume jewellery, mostly imported from China and India, Chand and shopkeepers said.
Escalating food prices have multiplied the cost of wedding banquets, with economists blaming Pakistan's general economic downturn and militant attacks.
Independent economist A.B. Shahid said such hurdles, including ineffective government policies, may prevent Pakistan from meeting the official 3.5 percent growth target this fiscal year, which ends June 30.
Taliban and Al-Qaeda-linked extremists have carried out a two-year campaign of attacks that have killed more than 2,400 people in Pakistan, a country of around 167 million people.
"Terrorism in our country has highly affected our economy. Our people cannot spend much and this situation could persist until we succeed in curbing militancy," Shahid told AFP.
Pakistan's economy grew by two percent last fiscal year, the lowest rate in a decade, but even that level may not be attainable this year, Shahid said.