Mixed technologies radio.

[Murphyv310]

One of the last products made and marketed by the old EMI company was a portable radio which employed three low consumption valves and two OC72 transistors.

I suppose done that way because the three transistors that would be needed for the signal stages, were to costly?

It has other benefits.
The use of a class B output stage with transistor output reduces power consumption on lower volume levels than a DL96 will have on the HT battery.
HT batteries were expensive so removing the output valve will greatly reduce costs for the consumer, a big selling point. Low voltage batteries were much cheaper plus the filament current saving as well.