(this is partially covered in The Practice of System and Network Administration's chapter on desktop machines)
Basically, consumer laptops use the cheapest video chip, sound processor, etc. that the vendor can find that week. A business-class laptop changes chipsets once or twice a year, on a schedule that is predictable. This gives you the ability to certify your applications with the new chipsets.
The business-class laptops are also significantly faster, more powerful, and more durable. You can buy the consumer laptops, but you'll spend more time listening to customers whine about how slow they are and managers will hear excuses like, "the project is late but it's my laptop's fault".
The real problem here is that the management people that ask this question aren't involved enough to understand these things. As Dilbert's boss once said, "Anything I don't understand must be easy to do." You might want to build up a comparison chart with them and make it an apples-to-apples comparison: show that the video card will be slower (in management terms: MS-Excel spreadsheets will display updates and scroll slower), that repair costs are going to be high (maybe you'll have to stock a "loaner laptop" that sits idle most of the time), etc. Let them be involved in building up the comparison chart. Heck, if it turns out that the differences are things that they don't care about, you might switch to the cheaper equipment!
More importantly: if you do this project with a manager, they'll be able to explain to the other managers in their language what the result is. That may be more valuable than anything else.