There is a great discussion in the freelance community about how to calculate the price of a project. The value-based pricing is definitely worth consideration. But it doesn't fit all projects. Some freelancers doesn't have the guts to offer the value-based pricing to his/hers client. I may be one of them.
I used to be a freelance developer a few years now. Here is my idea of hourly pricing.
Project cost / Pricing calculator
Another red flag could be when there is missing some 'Hello' of 'Hi' in the email from a client. But usually, when a client doesn't say Hi, he/she doesn't sign himself/herself as well. So let's say I summed it up in the signature red flag. Similar are typos in the email. I didn't want to make the calculator too long.
Have I mention that Calculoid is a service to create your own pricing calculator and place it to your website? A customer can calculate and pay directly the calculated amount.