
  would the fact that it's all comcast mean that they have their routers setup wrong?


Set up wrong? Yes, private addressing should absolutely be filtered within the interior of their network. But if they've been a bit sloppy then it's possible if the path is all Comcast- in carrier networks, especially sloppy ones like Comcast, private addressing is filtered at the edge networking diligently, but not nearly as much at the core or access portions. In your case it appears that the entire route is Comcast-only, so it is 'reasonable' that this might actually be forwarded to a destination also within Comcast that actually answers for it. It isn't a clean networking implementation, to be sure, and you did go from the Baltimore area to Denver and finally to Georgia, but it is possible within a complete "autonomous system" that allows for it.

Private IP getting routed over Internet
I noticed that my players would pay everything in gold. A simple piece of bread? 1 copper. "Here, have a gold and keep the change." They get into a tavern. A beer! Here, have a gold coin and keep the change. They would give beggars gold coins like they are candies. They make a donation to the church. 10gp. That's a stupid amount of money in fiction. But for them that's nothing. They always spend their money on the most expensive stuff in the tavern and would request the inn keeper to open the most expensive bottle of elven wine he has and the players will pay 3 times the price of that bottle. Why? We're rich we don't care!

Most of the time, NPC will have never seen a gold coin in their life. A inn keeper maybe. A farmer, forget about that. My players don't really think about the social and economical consequences of that and I'd like that to change.

First, I have no idea how I should have my NPCs react except having them jump like they won the lottery. That would just encourage the players to continue. I want them to understand this is weird, unusual and almost out of character. I don't want to punish them, I want them to understand that would be the equivalent of donating 25,000$ to the girl at Starbucks.

Second, how would the setting change? Suddenly there's this town where the PCs are spending money like they don't know what to do with it. And as a matter of fact..they frequently don't. In my settings there are no Magic weapon Wal-Mart. Magic items are special and you can't simply buy them in a random village.

Edit: Assuming I'm playing in D&amp;D 3.5 (which is not the case but it's irrelevant anyway because the system is not important. I play in a D&amp;D 3.5-ish setting). Also assume I follow the recommended money-per-level table. I couldn't find the D&amp;D one but the one for Pathfinder is similar. I usually don't give them the equivalent of the loot in money. I split the loot like this: 75% of the loot in item and the rest in a mix of coins and random objects.
