The bottom line here, for me, is that we play a game that exists solely within the confines of our mind. Things exist, not because they must, but because we choose them to be so. As such, if we choose them not to be so, they need not be so.
So that leads me to this: the idea of lazy module design only applies to those who lack imagination themselves. Nothing in a module need exist unless the person reading it chooses to agree with it. If you do not want there to be 2000 cp, there can be 2454 cp, or there can be none at all. What I find more interesting, though, is taking the module literally and then working with it, no matter how deranged it seems.
So rather than change the module, why not ask yourself as a GM, why ARE there 2000 cp in a rat's nest? How DID that improbable sum come to exist in such an innocuous location? You don't need to plan out every possible scenario in advance, but rather leave yourself open to allowing for those scenarios to play out as needed. Leave the 2000 cp where it is, and allow for the possibility that there IS a reason for it being there, and allow the PCs to explore that, should they so choose.
For instance, the party stumbles upon the rats, defeat them and search for treasure. They find the 2000 cp, and say, "What? Six rats have 2000 cp? Well that's highly unlikely."
Rather than agreeing with them, stare right back at them, and say, "It is rather odd that there are exactly 2000 cp. Would you like to look around more closely?"
They could find a seal, indicating that this was once the treasure chamber of a local bandit, looted of all except the least valuable (200 lbs for 20 gp? No thank you!). They could find that there is a secret passage that is held closed by 200 lbs of weight, and removing even a single coin opens it - it could also be a trap, and the secret passage is beneath their feet! They could discover that the coins are cursed, and that that a mage has been storing them here for future use, and is planning to distribute them at court. They could be ensorcelled, allowing the spellcaster to listen in on any room in which they are placed. The coins might not be coins at all, the pile could be a previously undiscovered offshoot of mimics. They could be an illusion, designed to confuse adventurers long enough for something to respond to a silent alarm tripped by their probings.
My point here is, that there are an infinite number of reasons why exactly 2000 cp are sitting in a rats nest, and only the GM has the power to make it interesting, or boring, not the game designer.
In general, especially when I'm in a Sandbox/Hexcrawl/Megadungeon, I try and allow the players the latitude they need to steer the game in a direction that they find interesting. Even if I have a general idea of the direction that a game is headed in, that doesn't mean there can't be distractions along the way. If the fact that 2000 cp are hidden in a rat's nest, then why not give them a story to chase?
I want to encourage creativity in my players. I want them to find solutions to problems I didn't realize existed. I want them to think of alternative solutions to problems I did come up with myself. Just because I had thought of one particular way of solving a scenario doesn't mean that if they come up with a better one it's invalid. Hell, even if it's not as good as mine, I'm still not going to shut them down - let's roll with what you've got, and see where it takes us.
Rather than saying, "No", ask yourself, "Why Not?"