I think it can vary a bit when it comes to the trade stores, the big ones like Reece and Tradelink are generally no better than Bunnings, ie just looked up the price for some 25mmx50m poly at both Reece and Bunnings and Bunnings is $59 and Reece is $79. If I go into Reece though and they give me trade prices due to my account, I'll get a cheaper price than Bunnings, and that is often the issue, it often comes down to how much the person behind the counter likes you if you don't already have an account, with Bunnings you know what you are up for. On the other hand, the local independent Nut and Bolt places beat Bunnings hands down in all price, service and availability.   

A 55m roll of 25mm poly pipe is $84 at Mitre 10, it’s $55 at Bunnings.
A 6m length of 90mm storm water pipe is just under $15 at Bunnings, exact same product (same brand) is just under $20 at mitre 10.

All wholesalers and “plumbing” stores are long closed by the time I’ve finished working my real job and gone to pickup the bits I need for my after hours jobs.
Shopping at Bunnings at 7:30pm on a Tuesday night is a pretty stress free experience...

Agree Pete, as a "part time" plumber these days I usually end up at Bunnings. Just last weekend I went to Reece and got some press fit fittings and a roll of pex pipe. No real discount offered as I don't have an account. Went to Bunnings on Sunday and seen they have a new push fit range of fittings for pex pipe, the prices were comparable with Reece.
I have spent a few hundred thousand dollars at plumbing supplies in my day and know that they have tiered level pricing, the more you spend the bigger the discount. It always left me scratching my head about the nature of that model, big players could buy cheaper and the smaller operator no so cheap. Always made quoting competitively difficult.
These days when I walk into the plumbing shop I am treated no different to the handyman, unless I ask ( which I will). This is in part that I am a new by up in Qld whereas in NSW I frequented my preferred store and so was known to staff.
Part of the appeal with Bunnings is you can touch n feel the goods, not so at the plumbing or electrical store as you are assigned a position on the customer side of the counter.

personally I think thier range is not that good...yes they sell a lot of different items, but if it's plumbing gear I want I'll go to a plumbing supply store like Tradelink who has a bigger range, if it's electrical I go to an electrical supply store like CNW that has a bigger range, if it's timber I find Bretts has a better range overall or Finlaysons or even specialist sawmills like Enrights at Beaudesert. Bunnings used to have a bigger range, over the years they have culled what they sell down to thier biggest selling items...very smart business move, but rubbish if you want something other then certain items, they thrive on disorganised people dropping in regularly to buy stuff from them over planning ahead and getting gear much cheaper from elsewhere.

A 55m roll of 25mm poly pipe is $84 at Mitre 10, it’s $55 at Bunnings.
A 6m length of 90mm storm water pipe is just under $15 at Bunnings, exact same product (same brand) is just under $20 at mitre 10.

All wholesalers and “plumbing” stores are long closed by the time I’ve finished working my real job and gone to pickup the bits I need for my after hours jobs.
Shopping at Bunnings at 7:30pm on a Tuesday night is a pretty stress free experience...

Hahahahaha,
Yeah, well, looked the goods for a few minutes.

but they don't really pass the savings onto customers...you can buy electrical and plumbing gear way cheaper at wholesalers, well worth the effort to go there over throwing hard earned dollars into Wesfarmers pockets.

Correct, having dealt with them for many, many years I know the type of margins they make and the below the bottom line costs involved with dealing with them.
Despite this I find myself in the stores from time to time.