> The record for the most number of satellites launched in a single mission belongs to Russia, which sent up 37 satellites in 2014.
Also, it's not exactly a feat. If someone really wanted, they could stuff a rocket full of nanosats but I imagine there's more risk in launching that much at once. (They could be released in sequence but still, more chances for something to go wrong.)
"the PSLV's payload to LEO is 3.25 tons. Wikipedia gives the cost of a launch at 15 million USD so that gives about $4600/kg to LEO. For context, that's nearly twice as expensive per kg as a Falcon 9 launch but they're difficult to compare because they serve different launch markets."