[Cheesecake]

Best advice: Bribe Me.
If you aren't sure about the price just ask for bribes.
Once a few people offer the price you'd like just use an average around it.
Like for instance.

You have three customers offer: 7.5k // 8k // 9k receptively for are like the second piece. The average of the three would be around 8.1k-8.2k so a good place would be 8k for the second style.

Let people offer for art, instead of asking for prices, because I'd get confused taking a bunch of different people wanting this price and that price.