1. Most people are either in the camp of prioritizing their time/comfort, or their wallet. Only a minority of people think about opportunity costs. It's too abstract. The people you mention, who do think about this way, are usually also capable of calculating the cost themselves. It's not an advanced equation / algorithm.
2. "Premium version" -- I don't like this.
3. Streamlining the whole travel experience to include parking, transport, hotel etc. makes it more useful, so it's interesting from this perspective.
4. Since you've noticed the many flight comparison services available, what is your analysis of the market? How do they acquire users? How much is a user/customer worth? Having one additional non-proprietary feature than another service, is not enough.
2. "Premium version" -- I don't like this.
3. Streamlining the whole travel experience to include parking, transport, hotel etc. makes it more useful, so it's interesting from this perspective.
4. Since you've noticed the many flight comparison services available, what is your analysis of the market? How do they acquire users? How much is a user/customer worth? Having one additional non-proprietary feature than another service, is not enough.