It's 30% of the wholesale cost, which is quite different than the retail cost.
The cost may be paid by the producer, the importer, or the consumer. In competitive markets, there is more pressure to keep the selling cost down. A product selling at 5x markup would be a 6% increase in cost, assuming the consumer actually paid the full amount.
Consumers also have the opportunity to substitute with another purchase that does not have a tariff, such as a similar Made in the USA product. They could also just realize they don't need to buy that Chinese crap, anyway.
Tariffs are, at worst, a small voluntary tax for exercising the privilege of buying something made abroad.