The reason lab PSUs are so expensive is that they are incredibly stable. A regular cheap power supply will provide a sort-of stable voltage, but there will be a

The reason lab PSUs are so expensive is that they are incredibly stable. A regular cheap power supply will provide a sort-of stable voltage, but there will be a loooot of noise on it. Meanwhile, even a basic lab PSU will guarantee the output voltage to within a few mV, no matter what you throw at it. This allows you to completely rule out the PSU as a potential source of faults.