Silica Gel ~$4 a bottle, lasts you between a few weeks to a few months depending on usage, add a digital hygrometer to ensure you're at the right humidity == ~$20-30 == total startup costs up to $70. A lot of trouble making sure u have the right amount of silica gel, replacement etc. Also, a $20-30 box might just barely fit your DSLR body + 1 lens + some accessories.
Dry cab typically comes with built-in hygrometer, doesnt use more electricty than a light bulb.