Review on Yaweco Toothbrush Heads Soft Refill by Erin Romero

I bought this brush and am happy with its performance, I really like that only the head has to be thrown away. However, the price for interchangeable heads is unrealistic. The whole brush is under $7 and the heads are over $14. I understand you get multiple heads, but how can it cost more to produce and ship the heads than the cost of the entire brush? Either this is to prevent only the head from being replaced, which seems counterintuitive, or the manufacturer benefits from the fact that the customer is tied to the product.