Hi, this is a really broad question,
1)
From a pricing perspective the prices vary depending on your location, if you are in Australia i would be happy to help for the rest of the world we may be able to help but you would perhaps want to find a local partner
Microsoft can normally suggest a partner for you as well
From a BI perspective you have a ton of options, out the box you can use NAV reports, SSRS (SQL Reporting server) reports, Excel reports using Jet Express, these are all your included options, then you can look at add on BI tools like ZAP (I mention this one because i have worked with it before) and many, many others
As NAV is based on a SQL database you can pretty much use any reporting tool however some like ZAP were built to work with NAV and will be faster to get up and running
2)
The HR question is really difficult, with the exception of implementing full blown warehousing where there was none before i have found that staff requirements actually go down due to efficiency improvements, this however wont hold true when you implement controls and management where there were none before, so to answer this depends from business to business
you can expect a lot of efficiency improvements and perhaps some more work, this will possibly result in the need to move staff around but this can be better identified on-site
3)
A couple of parts here, the first is licencing cost and this is pretty specific to countries
On the maintenance side i find that companies that skill someone up internally can normally get away without needing much external support, especially as a lot of the reporting requirement can be handled internally
On the flip side there are companies who like getting external help desk support for queries
This will also depend on the number of users as well what areas of the system you are using (Financials only, Warehousing, Manufacturing, Jobbing, Service....etc)
Hope this helps, shout if you have any other questions and i will try to assist
Cheers
Nev