SQL has to do meta-data lookups whether or not * is specified as it has to find the types and the column lengths.
The reasons to not use select * are more around only retrieving the columns that you need and not returning all of them out of laziness. It's also so that code won't break if a new clumn is added to a table. finally, select * makes creating covering indexes almost impossible.
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SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
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