What are the common add-on charges in whole-house customization?

Add-on charges usually hide in several places: first, hardware upgrades—DTC is standard, and switching to Blum or Hettich requires paying the difference; second, door panel processes—upgrading from double-sided melamine to PET, baked paint, or real wood veneer involves obvious price gaps; third, cabinet body boards upgraded from E0 to ENF or eco board; fourth, functional components—drawers, pull-out baskets, trouser racks, light strips; fifth, on-site conditions—uneven walls require base leveling, and removal of existing cabinets is not included in the quote. Kitchen cabinets are calculated by linear metre: basic configuration is 900–1,000 yuan/linear metre in Beijing and 765–850 yuan/linear metre in Baoding, Langfang, Xiong'an and Zhuozhou; upgrading to ENF eco board cabinet bodies + PET doors is 1,300–1,650 yuan/linear metre in Beijing and 1,105–1,402.5 yuan/linear metre in Baoding, Langfang, Xiong'an and Zhuozhou—the tier difference is money.