It is not just the printer but the calibration equipment you need to ensure you have a consistent print quality. Typically an A3+ printer from Epson or Canon can be had for around £500 but ink costs are high and so is the paper if you are going for the archival type. However you need to factor in monitor to print calibration and the fact that not all monitors can be calibrated properly. Typically a full setup would be a calibrated Apple, Lacie or Eizo monitor coupled with a profiling kit to keep the monitor calibrated. A printer calibrator and a daylight viewing station for checking prints plus printer and inks. Depending upon your throughput printing yourself could be much more expensive than a pro-production house but you will be in full control of the process. Goto a specialist for the monitor and calibration stuff such as www.nativedigital.com they can really help you achieve what you want. Printers can be bought from whoever is cheapest but HP, Epson and Canon lead in the high quality stuff with Ricoh being a good choice for specialist object printing.