Here is a customer point of view for you. If I pay somebody to do whatever work for me, I would like to know the price for the materials and where he is going to buy them from. If I can buy them cheaper, I would rather do it myself.
Most of the tradesmen don't mind discussing this. But there were some guys who gave me a quotation of £300 for the materials to change some gutters. All the materials needed for the job, including the screws, cost less than £100 at B&Q. And I told them in advance that I want it done in the cheapest possible way. Guess if they got the job.
So, you're an electrician, and you've worked out that you need to make £200 from a job so that you can cover all your costs and have enough left over to pay the bills, feed your children etc.
You make some of that £200 from charging for your labour, and some from materials markup.
If your customer takes away the latter, what are you going to do?
Let's see.
Mr Sparky needs to make £200.
The retail price for the materials is £100. He gets a 25% discount at the wholesalers.
You do not.
PRICING MODEL A - WITH MARKUP.
Materials £75
Markup on materials £40 (thus making them
appear more expensive than you can get them for)
Labour £160
Total £275
Your spend on materials £0
Overall price to you £275.
PRICING MODEL B - WITHOUT MARKUP.
Materials £0
Markup on materials £0
Labour £200
Total £200
Your spend on materials £100
Overall price to you £300.
Since Mr Sparky won't be able to get his mortgage company, the supermarket etc etc to take less money if he makes less, then if you take away his profit from materials then he will add that back in to his labour costs - the alternative is homelessness and hunger, and he isn't going to opt for that.
Unless you can buy materials for less than he can your model is always going to end up costing you more money.