I've received a few emails about the following light source question, so I think I'll just post my response here so that everyone can see it. I think it is something that I should clarify in the official rule book eventually. :-)

Also the question about the bartering system is a good one. If anyone has tested the limits of my bartering system and has discovered that it is broken (ie. too easy to abuse to amass large amounts of wealth) let me know.
Hello there!
 
First off, I just want to say how awesome the Castle of Ravenloft reversion is. Your reversion brought my Brother in Law back and myself back into D&D. 
 
We did have a couple of questions however.
 
1. For selling items you state it is a DC check of 10. I'm not sure if we missed something, but you get an additional 25% for each roll above 10 based on which skill you use right? I'm sure that we are missing something because if that was the case you could run into a scenario were you could sell an item for infinite value. (If your skill was already above 10 for example.) We were hoping you'd be able to clarify the rule for us. (We're also rusty with many 4E rules so we may be missing something simple.)
 
2. When exploring with no light source, are you still able to uncover tiles? We've been playing that when you reach the edge of a tile that's when you flip it over. (Sort of like the standard boardgame rules.) Is this how it was intended?
 
Hope these questions aren't too much of a pain for you. Once again, I want to say how grateful we are about this reversion. 
Thanks for the complements on the Reversion! I love answering questions because they make me think about (and re-think) my rules and try to rationalize them.

Regarding your questions: With your question about selling items, you have found an aspect of the rules that I included, even knowing that there was the possibility of selling an item for a very high amount. So, it isn't a mistake, although I admit that I haven't play tested that aspect significantly to see if in actual play it could be greatly abused. Here's my thinking:

First of all, the item values as shown on the item cards are only a fraction (I believe it's around a 1/4th, if I remember correctly) of what they Player's Handbook says they're worth. So a player who doesn't choose to engage in bartering is only getting a small percentage of what the item is actually worth.

Second, when a player does engage in bartering they are only allowed 2 failures before they must stop attempting to barter that turn. In other words, there is a chance that the player won't get very far with their bartering efforts before the rest of the game intrudes upon their village time and forces them into the dungeon again.

Third, even if a player has a skill of 10 or higher in Streetwise, Diplomacy, Bluff or Intimidate, they still will fail if they roll a 1 on a d20. Not a high chance of failure, but still a chance.

Finally, part of my rationale is that if a player who is level 1-5 (the level of this adventure) has devoted a significant amount of skill points into one of these skills, they should be rewarded with both the financial and role-playing opportunities present in bartering and (perhaps) getting inflated values from their sold items. I ask you: Why not let a level 3 character, who has a 10 or higher Bluff skill, cheat a village merchant out of some gold? :-) Also, don't forget, a player has the choice of not bartering beyond a reasonable level if they so choose.

And, regarding your question about the light source: Yes, if you have a candle or no light source (other than the ambient light from the high windows of the castle), then you reveal other tiles by moving to the edge of the tile you are currently on. I think I need to make this more clear in the book because you aren't the only one who has asked about it.

Please feel free to send more comments or questions. I'm glad you and your brother -in-law are enjoying the game!

Best regards,

Chris