considering bulk purchase of android OS tablets for 150 field staff

[foibles]

My employer has approximately 150 – 250 personnel working in a field-based capacity....reading meters, performing asset inspections and maintenance, doing various odds and sods.
They are the last mid scale organisation in the known universe to be supporting such processes using decentralised paper based processing.
I have discouraged my employer from considering the procurement of 150 iPhone 5s....and then procuring an app which may support these processes (was not a justifiable investment case).
I would however like to do them the justice of considering more appropriate, more cost effective, more practical solutions.....such as fairly generic, unspectacular Android tablets on which we can have 1 or 2 android apps built.
Our requirements are pretty simple;

• A reasonably robust piece of hardware
• Camera capability (does not need to be leading edge 9 trillion pixels, etc)
• Screen size somewhere around the 7" – not too much of a concern
• Availability of accessories to help protect – rubber casings, etc
• More recent android OS or we'd even contemplate MS Windows
• As yet unsure as to WifI vs 3G – our guys are working in rural and remote areas, so 3G is almost certainly what – and all – that is required.

Above all – we are pretty cost focussed.
Has anyone been through a similar contemplation and – if so – what were your outcomes?
Is a bulk price of circa $150 per tablet unreasonable?