Greenhouse cost varies because projects differ in size, frame, covering, ventilation, foundation or anchoring, doors, insect net, irrigation, crop-support hardware, automation and installation scope.
Location adds another layer. Transport, access, wind exposure, drainage work and site preparation can change both material and labour requirements.
A low headline price can exclude items that become necessary during construction. Compare quotations using a clear BOQ that shows what is supplied, what is installed and what remains the client's responsibility.
For a useful estimate, provide the site location, proposed dimensions, crop and desired control level. A project-specific quotation is more meaningful than a universal advertised rate.