Don't worry about it. Not every monster has treasure.
We have a house rule that mundane items of creatures that aren't worth much go into a general fund called "beer money." After the adventure, the party has 14 goblin spears, 24 kobold shields, and 2 dragonborn 2-handed swords? Congrats. That will pay for food and lodging until next adventure begins. Deals with a lot of pesky petty details.
How often is that carriage going to affect the adventures? Not very. Same with the horse. Sure, let them have a traveler's feast table and a throne of command. How often are they going to carry those massive heavy objects with them? Yeah, they might stuff one or the other in a bag of holding, but then where are they going to store the dragon hoard they just found?
Actually, the horse and carriage are great for when they have to travel between vastly separated encounters. And, if the carriage is that valuable, it could well attract bandits! After all, only someone wealthy would have something so expensive.
DMG has a pretty good set of examples of treasure packets.