There are two important features in a signal generator that make it useful for receiver repair and troubleshooting.
A stable frequency output.
A calibrated output attenuator. One that lets you turn down the output to microVolts, calibrated to show how many.
And those are what drive up the cost.
Signal generators that won't tell you the actual level down to the microVolt are useful, but won't permit you to measure the sensitivity of a receiver. And if the frequency is only "close", it won't serve as a way to set SSB receivers on frequency with any accuracy.
The one in the Ebay listing only goes up to 25 MHz, not 27. The output level is not calibrated. The frequency readout is only approximate, but clearly better than the old analog dials.
A neat tool, but not intended for receiver alignment or troubleshooting.
"One accurate measurement is worth a thousand expert opinions" -- Admiral Grace Hopper