It's a difficult question, for almost all of us I think. Like you said, first I would go to the knifemaker's for sale forum here and get an idea of where you land in the market in terms of appearance, fit, finish, and materials. Be honest and critical of your own work, and look around a lot. It's easy to find one knife that doesn't look that great to you and say "mine is totally better than that!" One piece of data does not a trend make. Keep in mind that your name is part of the equation, so if you're new, you might have to charge less for a knife of equal quality than someone with an established reputation.
Next, you need to do some math. Figure out your expenses in steel, handle materials, abrasives, heat treat, etc and figure out your total investment in a knife. Figure out your hours, and ask yourself how much you want for your time. This part is tough, because if you're new, it probably takes you way longer to make a piece than someone else. For evidence, watch Murray Carter do a perfect hollow grind in 2 minutes in his POV video. So, you might not be able to pay yourself anything close to a reasonable wage at first and still price your knives at a level where anyone will buy them. From there, you just keep getting better and faster until it works out.
That's the long answer, the short answer is yes, eventually you will develop a formula just as you've laid it out. I do $X/blade inch + $X for thicker spine, tapered tang+ $X for multi-piece handle. I work in all pretty comparable materials now so I don't monkey with the small variations there, pretty simple.
Tracking time for each specific knife is not super practical, since they get made in batches for many of us and nobody wants to pay that much attention to the clock. You also need a way to quote a custom knife fairly and consistently, so developing a formula like this is kind of crucial if you're going to take custom orders.