I dont understand this line , we have imported power inegration ICs and made DC/DC converters with that and it works with good performance do you mean one should ALWAYS buy the metal cased high priced products ?

1) You are not responding to what I said "Fine, but hold those posts till you have measurements that show stability, efficiency and heat being as good as a 'storebought" one. "
2) I never said anything about "metal cased "
3) $10 for 24 to 5 @3A is hardly "high priced "

Erik