You've already received excellent responses. What I will build on is the higher level structure when approaching problem solving (i.e. after asking clarification questions and understanding the objectives).
You should start with thinking about how revenue growth is achieved: organically or inorganically (or both). Under organic growth, you can achieve that through
1. Increasing the price, as you've mentioned
2. Increasing the quantity - either by increasing your market share with existing customers or by targeting new customers
3. Launching new products/services - could be complementary produts, or entirely new ones
4. Entering new markets
Out of the box answers:
5. Increase the utilization of your existing products - the toothpaste example is great. DM me for more details.
6. Target non-customers and make them customers - increase the entire market size
You can achieve inorganic growth through:
1. An Acquisitions - of companies or products
2. A Merger
Now that you've defined the high level structure, you cover all grounds to grow revenue and will not make the mistake of forgetting any points as you go along with the case, especially when the interviewer asks you how else could you grow revenue (under each category you could expand. Ex: licensing deals, contract manufacturing, commercial agreements etc...).
After defining the high level structure, you could then figure out where to start based on the case and your clarification questions to the interviewer and begin with the points mentioned by the other experts that have responded to you (analyze market, competitors etc...).
Hope this helps.