Firstly, woodwork is a hobby for me. I work in teaching/engineering, so my weekends are all about just enjoying being out in the shed, with the dog, pottering about - the money isn't that important. That's a long winded way of saying I don't do it as a business, and even if I didn't charge I'd still be making stuff, so in one way I kind of look at the payments as a bonus
Having said all that, now I'm finding that people are happy to pay for my work. A friend said to me "You're happy to pay the garage £70 an hour in labour to work on your car - why is your time worth less?". He has a point, so I work out the hours, multiply it by that, add materials, and that gives me a price that a business might charge. Then I halve it......and maybe take off some more.
Big point in my favour is I don't actually care if someone buys it or not. I'm happy to have it sat in the house for the next two years, eventually someone will like it enough to buy it.