Very few products and services in this world are commodities to the point wherein you just 'add up the cost'.
In fact, I can hardly think of a serious product or service quite like this. Not even cars are like this. You have maintenance, resale, insurance and financing to consider.
This idea of an easy, objective way to 'calculate costs' is never really quite possible.
There are usually going to be some degree of Apples-to-Oranges comparisons, situations wherein small issues make a big difference. You want a sales person to be there to make sure that your potential customer is aware of the options.
In addition, there is of course the 'Total Cost of Ownership' - meaning that much of the 'cost' of something is not apparent in the calculation. Training, support, etc.. On the far end of that spectrum you have the strategic issues such as vendor lock-in etc..
So, even just trying to establish a fairly objective 'true cost' calculation will be hard.
Next, you have the fact that most enterprise sales are not 'off-the-shelf' - pricing is subject to negotiation, which can vary a lot. This makes it difficult to set price.
Then, you have communications issues around a sale - these are complicated products, the last thing you ever want is for customers inputting some information, and getting the wrong numbers back, or the wrong impression. If there is any money involved, it's worth the time to talk to a sales person to smooth over issues.
Finally, is of course the sales organisations ability to pitch, sell and spin. Of course this includes the shifty areas wherein the team will want to sell a service even when they know they are not the best option.
So a 'raw cost calculator' is possibly just a big, risky bit of possible misinformation and lost opportunity to make a sale.
The 'technical' aspect of making a 'cost calculator' is completely mundane to the point of being irrelevant. In fact, Google Engineers might be too overqualified to even do such a thing.
I see a 'cost calculator' has having two completely different roles:
1) As a 'sales lead' - something new customers can input information into, which is going to almost assuredly give them a good perspective, but wherein the true and only purpose of the calculator is to generate a lead, so that a sales person can chime in.
2) A customer-centric calculator, for established customers that is tuned to their account status and discounts and let's the IT manager or business lead do projections on the service.