Q: I understand that there is "PowerPivot for Excel" and "PowerPivot for SharePoint". First one is free, but are there other limitations, like "just on Excel 2010 Ultimate", etc.
How much "PowerPivot for SharePoint" cost - what software do I need to buy and how much this software cost?

A:PowerPivot for Excel

There are 3 available Office 2010 versions that you can buy. Prices in US would be (store.microsoft.com/Category.aspx?CatId=210):
Office Home and Student 2010 - $149.99
Office Home and Business 2010 - $279.99
Office Professional 2010 - $499.99

PowerPivot for Excel add-in is free and will work on any of these Office 2010 versions. PowerPivot for Excel will not work on "Office Starter" version.

I assume that you do not really need to buy full Microsoft Office and it is enough to buy just Microsoft Excel 2010. But at this point I am not 100% sure if that setup would work, as PowerPivot add-in requires "Office Shared Tools". Excel 2010 pricing is a bit cheaper:
Excel 2010 - $139.99
Excel Home and Student 2010 - $119.99

I'll try to confirm if Excel 2010 is enough and I'll post my findings here later.

PowerPivot for SharePoint

PowerPivot for SharePoint requires:
- SQL Server 2008 R2 Enterprise Edition or higher
- SharePoint 2010 Enterprise Edition license

SQL Server 2008 R2 pricing in US can be found here: www.microsoft.com/sqlserver/2008/en/us/pricing.aspx
You could calculate pricing per Processor or per Server/CAL.
Pricing per processor is $27,495.
Pricing per Server/CAL is $8,592 and price for each User/Device CAL is $164.
Prices above does not include Software assurance.
So let's say you would like to run SQL Server machine on 4CPU box and you expect to have 500 users.

Pricing for SQL Server Option1:
Note: as this is "per cpu" licence mode, you could have unlimited number of users.

Pricing for SQL Server Option2:
$8592 + 500x$164 = $90,592

These are very approx numbers. Your licence price will depend on your agreement with Microsoft. There are different volume licence discounts available.

I had hard time finding SharePoint 2010 EE pricing. Based on description here (sharepoint.microsoft.com/en-us/buy/Pages/Licensing-Details.aspx), my understanding is that I need SharePoint 2010 server and then EE Cal licences.

On CDW website I found that server licence is about $5000. www.cdw.com/shop/products/default.aspx?EDC=2076079.

On CDW website I found that SharePoint 2010 EE Cal licence is about 80$: www.cdw.com/shop/products/default.aspx?EDC=2076504

So for 500 users you would pay $5000+ $500*80 = $45,000

I think this should give you very rough estimate how much this costs. I'll try to investigate a bit more and will post my findings later here.

You should also consider that SQL Server and SharePoint will be running most likely on different machines and you will need licence for OS on these machines, like Windows 2008R2 Standard Edition.