The fundamental problem is not "Cuba pays slightly more for its parts from China", the fundamental problems run much deeper. Cuba spent thirty years embracing a position as a resource colony for the Soviet Union in exchange for massive subsidies on their sugar exports (the Sovs paid 5x the market price for Cuban sugar) and invested that money - nobly, but not wisely - in raising living standards instead of the creation of an economic base that wasn't reliant on total vassalhood to a powerful state on the other side of the planet.

It emerged from the end of the Cold War with a well-educated and healthy population, but no real economic prospects with the collapse of the Soviet Union and its massive amounts of aid which subsidized the sluggish economy of the Cuban government. So what did the Cuban government do?

Nothing.

Fucking nothing.

Not wholly true, I suppose - they vacillated between encouraging private enterprise and cracking down on it, which, ironically, was more ruinous than just doing either alone. Fidel Castro himself admitted that the government policy royally fucked up in the 90s-2000s transitional period. After Fidel's death, Raoul also admitted that the agricultural sector of the country was ultra-fucked. After Raoul's retirement, the Cuban government has been hesitant to make fundamental changes to the government because the Castro family was what lent the government legitimacy outside of its socialist credentials - leaving them slowly taking on water and sinking in a mess several decades in the making.

As it stands now, Cuba is reliant on a meagre tobacco industry, rum, promising mineral rights to China, and remittances from the expats in the dreaded Yanqui Empire (the remittances quite literally outstripping the total value of Cuba's exports).