This is one of the best new lands in War of the Spark. It has a similar effect to Engineered Explosives, an artifact with extremely effective removal ability.
Currently, Engineered Explosives stands at $40 a piece for an original Fifth Dawn printing. While Blast Zone may not be as fast as Engineered Explosives, the effect still guarantees a pretty high price point for the new land as well.
The other reason why Engineered Explosives is so pricey is the ability to destroy tokens, which is something Blast Zone can't do, since it enters the battlefield with a counter already on it.
That is why don't expect it to rise over $10 a piece, unless players find a simple way to remove the unwanted counter.