No client is going to get a NEW system under 1,800 from me. I custom build them and Incorporate Data Transfer, Updates, Software install, AV, email setup/migration. I rather build my own as I can trust the builder "me", using only quality components.
Then the onsite factor of things they may need is another expense, say printer setup etc. Small inkjet printers I don't worry about but if they want to network a dedicated printer, that is another onsite expense. Same as shared files/mapped drives etc.