The UCS series has consistently been expensive, but they were usually really expensive compared to the majority of sets available from LEGO. The vast majority of sets released in 2007 were much smaller and cheaper.
Whereas now there are multiple $500+ sets on sale concurrently, multiple sets that have multi-thousand-piece part counts. It's undeniable that in the last 10 years LEGO has significantly leaned into serving the adult market.