But " inexpensive" ? Certainly NOT, according to Harley's price lists . I don't believe that Harley's annual rehashes of its previous century "technology" justify today's price tag as far as the engine, tranny and chassis are concerned.
There is nothing wrong with a pushrod valvetrain and 2-valve head. it is compact, inexpensive, and can do many things better than an OHC 4-valve design. Especially when low rpm torque is a priority over a wide powerband.
The problem is the combustion chamber and port shapes.
Look at the modern Chevy LSx engines. Very efficient and compact.