A spectrophotometer is a fairly easy DIY project. Nowadays, they are done with a reflective diffraction grating, some slits and a light sensor. The sensor is e

A spectrophotometer is a fairly easy DIY project. Nowadays, they are done with a reflective diffraction grating, some slits and a light sensor. The sensor is either a line CCD or a DLP with a InGaAs Avalanche Photodiode (APD). The price is mostly due the sensor. Line sensors can cost from tens to thousands of dollars (see hamamatsu S7030/S7031 CCD). To measure absorbance, a wide spectrum light source is needed (that's why OP's spectrometer has tungsten halogen and deuterium arc). The sun, in some extent, also works for that. To measure emission, you don't need a light source. The difficult part is doing the calibration. That can be done with neon light, mercury vapor, etc.