Why are large planters (20 inches and up) so expensive?

This is a recurring complaint across high-trust r/gardening threads, where shoppers report struggling to find attractive 24- to 30-inch pots under $50–$100. Double-walled resin planters like the Sunnydaze Anjelica and composite designs are frequently recommended as lighter, more affordable alternatives to ceramic, with reviewers noting they stay manageable to move when not filled with soil.