It may not have been the only reason, but cost was absolutely a major real reason. In a planned economy, cost does not disappear. Skilled engineers, specialized materials and equipment are all still scarce. Semiconductors are literally the most sophisticated manufactured products and require the most complex supply chains. The Soviet Union was notoriously bad at coordination between ministries, state agencies, design bureaus, and factories. Semiconductors are probably the single worst industry for the Soviet model.

Maybe in theory, they could have lobbed enough bodies at the problem to make it go away. But they simply did not have the resources.

Of course in any economy, there are scarce resources, and skilled labor is certainly one of them. What I'm specifically arguing against is the assertion that in a planned economy, the existence or lack of a customer base would in any real way impact the allocation of those resources. That's not a helpful way to analyze the decisions of the communist planning committee.