As a salesman and consumer I see both sides of the argument here. I will always expect and be willing to pay more for expertise and better service. I don't see a problem with that, training takes time and costs a lot of money.
As a salesman I see it as my job to show the client that the service and expertise that he is receiving is worth the additional money they are paying. Part of this comes down to knowing your market and more specifically the customer you are dealing with. For some price is all important and others just don't want problems and will pay extra to ensure that any issues will be taken care of.
I will never rip a customer off but not every customer pays the same price, my job is to find the highest price that the customer is
happy to pay. If someone knows exactly what they want and doesn't need help or advice then they pay for the product. If they will need my expertise before and/or after the sale then they pay a premium for that. The advice is a service, just like mowing a lawn, and should be paid for.
What really bugs me is when a customer milks you dry for information before the sale and then goes to someone else to save themselves a couple of bucks. If they can save a significant amount then that's fine, it means I don't really know my market, but not for a few bucks. Those types are really just mean spirited, tight-arsed scrooges and deserve everything they get (and generally get everything they deserve in the end.)
Once you begin asking for advice, this is distinct from asking for specifications or details, I think you have some obligation to purchase from that supplier. The level of obligation is dependant on the amount and level of advice you get. The more advice the more you should be willing to pay. Once the price differential exceeds your obligation you are free to shop elsewhere, it shows that the seller doesn't know his customer even though he may know his product.
Just my 2 cents worth anyway.
Travis