Proprietary - this is manufacturing a computer system with parts that are made by or made specifically for the manufacturing of that particular computer system. In many cases, standard parts will not work in the proprietary computers by design. This makes out of warranty replacement of parts and repairs very expensive. Computer A and computer B have all the same specifications. A lot of times it is because of the design and quality of the computer.
Integrated computers are generally less expensive than modular computers.
Integrated proprietary computers are generally less expensive than integrated computers. Integrated proprietary computers built with low end parts are generally the least expensive. Keep in mind with computers you get what you pay for. Reading the specifications of two computer systems on a piece of paper can be misleading in the quality of computer system you purchase. These charges are also applied to some if not all warranty repairs.