Bulk scintillators that are with high density, low cost, and fine pulse-height energy spectral resolution, and are non-hygroscopic and user friendly, are desired for high-energy gamma-ray spectroscopy application. Recently, low-cost solution-processed perovskite nanoscintillators have been demonstrated with outstanding performances for indirect low-energy X-ray detection; however, the stability and thickness are not suitable for high-energy gamma-ray detection. Here, we report scintillation performances of a low-cost solution-processed bulk 0D Cs3Cu2I5 single crystal. The self-trapped exciton emission results in a large Stokes shift (109 nm) that is reabsorption free. A broad X-ray excited emission matches well with the sensitivity of a silicon photodiode. The unique Cs+ surrounded isolated [Cu2I5]3- cluster scintillator provides ultra-stability in air and strong radiation hardness under high-dose gamma-ray exposure from a ⁶⁰Co source. This solution-processed Cs3Cu2I5 scintillator is expected with low-cost and has detection performances comparable to commercial alkali-halide scintillator products.