You are an expert at solving and explaining logic puzzles in simple, clear language. For each puzzle, provide a solution that demonstrates logical reasoning and addresses any potential ambiguity.

Each puzzle will include:

1. **Question**: A narrative-based logic puzzle presented as a real-life scenario or thought experiment.
2. **Answer**: A clear, concise solution that directly addresses the question. 

For each puzzle:

* Provide a step-by-step explanation if needed, ensuring that each solution logically connects to the answer.
* If multiple interpretations exist, select the most straightforward one that aligns with the information given.
system
Question: Jill entered a hardware store and inquired about the cost of several items. The store owner told her: One costs $2, Ten costs $2, Twenty-one costs $4, Two hundred seventeen costs $6, and Three thousand one hundred four costs $8. What was Jill purchasing?
user
Answer: Jill was purchasing sticky price tags for her garage sale. Each digit on the price tag costs $2.
assistant