Hi BFoelsch,
It all comes down to where it was designed and where it was produced. The design costs are 'non-recurring expenditures' (NRE) and must be amortized over the years of production, per unit. So if they don't have the expertise for a switcher design in house and they would have to use outside services they might have figured the NRE would be too high. EMI testing also factors into the NRE number and is expensive. These kinds of supplies aren't exactly large volume products since they are mostly bought by companies and hobbyists, not the consumer. Which means NRE weighs much heavier than for, say, an MP3 player.
Production costs depend on what's there locally. In the US a custom transformer or even an off-the-shelf one would be pricey. That can be different in other countries where labor is cheaper. Also, if the device uses a transformer that was meant for automotive battery charging it would be very cheap because such chargers are a true consumer mass product. Mine was $29.95, with a heavy transformer in there and lots of big accessory cables. Take away these cables and apply their cost towards an electrolytic cap plus a linear regulator, and bingo.
Switcher aren't always the optimum solution. Most PWM chips are in the $1 range and even I have mostly resorted to discrete designs for switchers and converters. Simply because it ended up to be cheaper. Most mundane logic chips cost under 10c and transistors are also just pennies. Just imagine, a product that retails for $40 and must be transported in from Asia has to be produced under $10. Else it won't likely make a profit.
Regards, Joerg
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