There are always some legit reasons for the drops (skyrocketing prices are usually a bit more hard to justify). Here are some for the ones you mentioned: 10187 - Yes, the 10187 prices really started moving when the Camper came out. There were probably more people who wanted this set after the Camper came out than wanted it during its retail availability. 10184 - The Modular Town Hall, and Cinema sets have made this once seemingly amazing set seem much less so. There would likely be a gas station modular as well, but the environmentalists may have killed that possibility. 10190 - The most rare piece (5 Dk Blue arch) was made available in the 10235 set (which immediately gave the set an $80-$100 haircut). Plus, it is a bit ugly, and lacks the official modular stamp. 4954 - Since 2007 Lego has continued to produce many Houses and Modulars that far exceed what this set had to offer - In 2007 it was incredible, but today - not so much.