3,938,383 Bytes - fee: ZERO
it costed them cpu cycles to do the proof of work to get that block into the blockchain though. so it wasn't free. yes i guess they got the block reward but they didn't include peoples transactions so they missed out on whatever those transaction fees would have been...
what it costs a POOL stratum owner. vs a asic owner are 2 separate things
asics do the PoW and they never see the transaction data. it doesnt matter if the block is 0.0001mb or 4mb an asic processes the same data length
a pool stratum owner. only needs to manage 1 sig operation and no validation checks on the dead weight
this a a big difference to handling 2000 transactions with thousands of sig operations and validation checks