Thermal Camera can only be used to locate electronic items powered on. If it is powed off, there is no heat, then thermal camera can not find it.
NLJD can be used to locate any electronics no matter it is powed on or off. The working technology is quite different. NLJD is also called harmonic radar. It emits a fundamental wave signal, receives the 2nd, 3rd or even higher harmonic/combined wave echo signals re-radiated from the target, and detects them. It is a Radar system for target judgment, identification and detection.
When it comes to cost, there is big gap.
I think less than 1K USD, you could get a very good thermal camera with high ir resolution, from those top brands.
While, an entry level NLJD equipment, just for B2C cost, should be over 5K USD. Advanced NLJD would be over 10K USD.
Because of the high cost, you would see only high-end organizations would use NLJD, such as government, police, military would use NLJD, or some service companies who offer security services to those rich people.