Q:

Agile and increased costs

The digital function of the organization is attempting to adopt the agile methodology and this is causing an issue with the perceived increased in costs when due diligence is performed on the initial estimates.  
For example, the vendor pitched the platform at (let's pick an arbitrary figure), $100.  When the technology team was engaged to evaluate its implementation, it was discovered that the deployment would entail hardware, installation, integration support, maintenance, security, etc costs have now blown the initial estimates.  
This has resulted management questioning the role the technology team plays since each time a project engages the team, costs increase significantly.  
There is clearly a lack of understanding the requirements and generally most of the vendors don't include or account for the additional requirements since it sits outside their remit.  
The technology team has invested significant time and effort is describing the increased costs however from a managerial perspective, the issue lies with the operational efficiencies of the team and not the lack of practices in capturing the requirements, understanding scope, the additional costs, etc. 
Is there a way to bridge this gap? 

A:

Agile approaches this from two perspectives: building trust between the team and management, and collaboration between the team and the vendor. 
I would bring the management to the team area for a while when they work with the new platform so that the management has a first hand experience on the problems the team is facing. 
In all the projects where I was working with a vendor we asked (and got) a representative from their side who helped with the integration.  This approach helped the team to understand more the product and collaborate more efficient with the vendor. 
Nevertheless, even with an expert on board it took more time than it was promised.  This should be something that may turn the management's perspective.  Based on my experience this is an eye opener, because the management learns from a "trusted" (it trusts the vendor more than the team) party about reality. 
Somehow you should find a way to show the difference between a presentation or a html page and actual integration to the management.  Or, and it can also happen, you can pitch a project in which you change your existing system so that it would be easier to insert new third party technologies.