Yes, the real world, where people don't burn in AC power supplies in production with $5,000 Keysight or Chroma loads, they use the least expensive way they can ... even just a resistor.
100W class-D stereo amplifiers are < $100 each. A bank of those with resistive loads could burn in 10 sets of speaker cables at a time. Could even do double duty burning in AC cords at the same time. So let's call it $100*100 + $1000 for miscellaneous cabling = $2000 to burn in 10 sets of speaker cables and 10 AC cords a week, or say 450-500 a year (mom and pop shop remember). Time to put them in and take them out is likely < 2-3 minutes per unit, tops. If we amortized the equipment in the first year, that is $4-5 / unit. $2-3 over 2 years. A system for interconnects would be even cheaper. If you have the resources in house to manufacture 50 sets / cables a week (or 10), then the extra few minutes to put them on and take them off the burn-in system is not going to be a burden. If I was doing 50+ sets a week, I would likely do something a little more sophisticated and lower cost on a per unit basis, not to mention less hungry for electricity.
Now realistically, running 100W continuously through a cable is likely far more stress than what anyone would do at home, so it is likely the time could even be shortened, even considerably for the speaker cables and you could similarly load up the interconnects much harder.
You don't have to be Apple to do mass production. For many companies, 1000 units/year is "mass production".
100W class-D stereo amplifiers are < $100 each. A bank of those with resistive loads could burn in 10 sets of speaker cables at a time. Could even do double duty burning in AC cords at the same time. So let's call it $100*100 + $1000 for miscellaneous cabling = $2000 to burn in 10 sets of speaker cables and 10 AC cords a week, or say 450-500 a year (mom and pop shop remember). Time to put them in and take them out is likely < 2-3 minutes per unit, tops. If we amortized the equipment in the first year, that is $4-5 / unit. $2-3 over 2 years. A system for interconnects would be even cheaper. If you have the resources in house to manufacture 50 sets / cables a week (or 10), then the extra few minutes to put them on and take them off the burn-in system is not going to be a burden. If I was doing 50+ sets a week, I would likely do something a little more sophisticated and lower cost on a per unit basis, not to mention less hungry for electricity.
Now realistically, running 100W continuously through a cable is likely far more stress than what anyone would do at home, so it is likely the time could even be shortened, even considerably for the speaker cables and you could similarly load up the interconnects much harder.
You don't have to be Apple to do mass production. For many companies, 1000 units/year is "mass production".