The honest floor is 50,000 BDT. That covers up to five pages, a custom mobile-first design, your domain and hosting in your own name, basic on-page SEO, Google Business Profile setup, a bKash/Nagad payment section, a simple self-edit admin, and the design-approval guarantee. The next tiers are 90,000 BDT (booking, blog, more pages) and 1,50,000 BDT (small store, Bangla + English). Fully custom builds start from 3,00,000 BDT. Payment is 50 percent advance, 50 percent on launch.
If someone in Chattogram quotes you 9,000 to 18,000 taka for a real custom site, they are using a nulled theme or planning to bill you again later — that is not cheaper, just smaller up front.