I was part of the founding team of a power electronics startup. We constantly tore down our competitors' products to estimate their costs, to see how they corrected design flaws between releases, and also to understand which component suppliers they chose to include (this is a proxy for passing their reliability testing).
• visit their website
• buying their product and looking it up the parts online
• talk to your vendors
For the last one, this is particularly relevant if you're buying in a market with few suppliers.