The following is the estimated nRF51 current consumption during advertising with the DCDC disabled.
Advertising 1:
TX power: +4dBm
adv interval: 20ms (minimum advertising interval in normal adversising mode)
payload: 10 bytes
application processing: 2ms each adv interval.
Average current consumption: 1794 uA
Advertising 2:
TX power: +4dBm
adv interval: 1200ms
payload: 10 bytes
application processing: 2ms each adv interval.
Average current consumption: 33,4 uA
Advertising 3:
TX power: +4dBm
adv interval: 1200ms
payload: 10 bytes
application processing: 0ms each adv interval.
Average current consumption: 25,7 uA
Advertising 4:
TX power: -20dBm
adv interval: 1200ms
payload: 10 bytes
application processing: 0ms each adv interval.
Average current consumption: 19,6 uA
With nRF51 third revision hardware, DCDC reduces current consumption with up to 20% during advertising, see the nRF51822 PS 3.1 figure 11.