The value of getting a good designer - v - a landscaper

Once again I've been drawn into a discussion forum ! This time concerning how a landscaper should go about pricing and quoting for planting plans.
Now there are a whole range of landscapers out there, those that belong to trade associations, APL,BALI etc, those that just like to do decking those that dont do block paving, the list goes on.
As a designer I like to think of myself as a 'whole of market' practitioner, meaning that I do not tie myself to one particular supplier of hard landscaping materials, keep myself up to date on current trends and new materials etc.Eg, www.woodblocks.co.uk who I discovered last week.
A good designer should also have a good knowledge of plants and hopefully the horticultural knowledge to go with it.
This brings me back to my starting point,being that the landscaper didn't have the plant or planting knowledge and was asking for advice as to pricing and quoting. I have absolutely no reason to doubt this particular companies competency or quality. But I think that a failure to bring on board designers at the beginning leads to lost opportunities for the client.
In my humble opinion a good landscaper will either have a ' whole of market approach and have the necessary Skills and experience OR they will have a designer with a portfolio of work to whom they will sub contract to.
If you are going to consider having landscape work done. Investigate a good designer in the first instance, it will probably save you money and get you,through the design process a garden That meets everything that you desired and everything that you didn't realise that you desired.