I have no near field experience with the X900 Series
but I have accomplieshed many high yield task with "small" desktop printers from epson with little efford
the machines are really cheap to replace
if ONE 4900 shuts down due to any malfunction you basically have no backup
if one of n desktop size printer shuts down you can still proceed.
I had the Pro 4000 and the Pro 4800 in my workshop and did print OVER 24 Liters of ink with booth machines within 6 month, i printed day and night all kinds of jobs and it was really easy to maintain both machines.
Later I sold the Pro 4000 to namibia and the 4800 to a client in austria
used 4900 either with the clogging issue or other malfunction I could buy even for 100€ in germany
i looked for some ended auctions
http://www.ebay.de/itm/281468115529
http://www.ebay.de/itm/111475600543
http://www.ebay.de/itm/131276374450
http://www.ebay.de/itm/111440835871
http://www.ebay.de/itm/141380512263
http://www.ebay.de/itm/111409758265
http://www.ebay.de/itm/131276374450
basically ~1.000 and you could buy a used but good condition