The very, very small print said that the monitor included in the picture was not included in the price. Many advertisers now use that same trick to make their computers appear cheaper than they are. Some may say that's fair. Today it's monitors they charge you extra for. Already mice are considered options with more than one computer manufacturer.
Most major brands do that to some extent.
They'll claim that the intention wasn't to fleece you. However, you still have to pay a fortune when you want an upgrade. Talk to somebody in the memory business. There are so many different types and models of memory to suit so many different models of computer. Olivetti had some lovely brochures for their M3000 series of computers.