Peronally, I think that would be really interesting! However, I see too many problems with it. I agree with marthajo1 about setting expectaions for customers, and with moydear77 about having to post quite a bit of detail to justify your pricing.
In addition, I think it would make people feel badly. Those who just can't charge high-end prices would feel bad (I see posts all the time about how people feel they undervalue their time) and those who do charge high-end prices might feel strange seeing that their customers might be able to get a cake for half the price they charge from someone else...
I know this is the trickiest thing, and that knowledge and sharing it with others are powerful! But this knowledge is just better obtained through doing research on your own- in your area, online, and by doing the math about what you spend on ingredients and what your time is worth. After you use that info to set your pricing, if someone's willing to purchase your cakes at that price- you did good! If you feel like too many people are walking away because of pricing- you know what to do.
Sorry for the long rant, but I just don't think it's a good idea for all of us to post prices, though we should all feel free to PM the creators to ask what/if they charged!