Is scavenging parts from consumer electronics for own commercial products, a good idea?
For a prototype or the first beta units, it's a fine idea. Your time disassembling the units will eat in to your profitability.
Bad idea for production. Many cheap consumer products have a short lifespan, so you'll end up redesigning your product when you can't get the product. Plus, cheap products use the lowest quality electrolytic capacitors which fail at an early age (within a couple years), especially capacitors in switching supplies.