My wife used to work for a tool manufacturer and our friends work for varied manufacturers of fixtures (lighting and plumbing). Sue36 is absolutely correct, if the SKU is the same, so's the item. Sometimes, the SKU can even change and the item be the same. The interiors of plumbing fixtures are not different within a brand name as you go store to store or over the internet. I.E. the guts of all American Standard toilets are the same for a model whether it's sold at HomeDepot, Lowe's, or PlumbingFixtures.com (made that name up). Browse locally, write down model numbers, and search for the best prices online. You'll probably get special order items faster by going online than HD or Lowes. And some items that are special order at the big box will be in stock at a plumbing supply company, but not for a better price. Lighting boutiques have been very dissappointing to me, the selections are so small that I don't even look at prices. They have stacks of catalogs to look through, but heck, why not just browse them online instead of at their showroom? If you find a light you like, but are unsure of what their "Oil Rubbed Bronze" looks like, try and find a local retailer or simply ask for a small sample from the company. And all from the comfort of your home, 24-7.

We were lucky in that our plumber's prices were right in line with what I found online. However, I think there is something to be said for maintaining the goodwill of the plumber (he's not exasperated if bits and pieces are missing, or other issues due to delivery), as well as potential warrenty type issues. Aditionally, our builder uses a local guy, and in this small town I'd call him if we had plumbing issues 4, 5, 10 years down the road- he knows his work, he can fix it back up, and I I'd rather not leave a bad memory. I also find it much more effective to go park myself in a store if there is a problem rather than deal with people online (if a part happened to fail down-the-line). Now, what this may be worth is up to you, and which items are worth potentially annoying the builder and/or plumber vs. other things you may want to do differently in your build.

AFAIK - if a company doesn't have a Nexus in the state, they don't have to collect state / local sales taxes. As a programmer, I deal with this every day - check out AVATAX.com (maybe Avalara). As a CPA I also deal with this occasionally. Just because a business is not responsible for collecting the tax doesn't mean that consumers are not responsible for paying it. This is a common misconception, sales tax is actually an abbreviation of "sales and use tax." Businesses are responsible for collecting sales tax, but consumers are responsible for remitting use tax. The use tax is basically a tax on any item that would have been taxed were it purchased through a local/state sales tax collecting entity that you didn't pay sales tax on (each state will have slightly different wording). Many states that also have a state income tax (22 of them, mine included) have a line on your state tax form for payment of use tax, and you sign your tax forms under penalty of perjury. Historically states have not bothered with use tax, however states are starting to change. E-commerce is simply becoming too large to ignore, business to customer use tax losses exceed $15 billion and that is nothing compared to business to business e-commerce.

Lauren, there could be a million scenarios to your situation and most will not do you any good. It all comes down to the person you dealing with and the practices how they run their business. You buying a home from a builder, you have a contract which probably includes listed items that come with the house. Any deviation from these items the builder can charge you anything he wants...and nobody can do anything about it... It's pretty much comes down to "take it or leave it". Most custom home builders that I know don't do that, it is all about the person you're dealing with and their reputation and in your case if they try to jack-up the price that much, this is not a very good practice. I will give you one example of a similar situation. A few months ago I was doing 3 basement designs and layouts for homeowners who purchased new homes in the same development of 13 homes...most homes still under construction, they the 1st-3 to move in. All 3 homeowners were telling me the same thing that its impossible to get anything from their builder. Anything they want to upgrade is quadrupled in price, i.e you want oak stairs $6k extra, you want crown molding 3k per room, etc Its beautiful close to 1m homes, and when I came to one of them the 2nd time, they had a contractor there building coffered ceilings, doing crown, trimming out a few openings, etc. Back to drop cloths, back to dust, back to painting, when everything could have been done long ago before the closing and the builder reputation wouldn't be diminished. Most of the homeowners who purchased this homes know each other, 8 of them out of 13 homes are friends and work in the same field, and the first 3 who moved in warned everyone else that builder is impossible to deal with and he won't budge on anything. That said, there is always a mark up on upgrades because it involves extra work and you endure extra expenses, but the mark-up is not to bankroll a homeowner, its reasonable and its priced in the way to be worth while for the homeowner and so they keep on smiling while they job moves along. We not living in the stone ages, today you give a price for something within a minute you can pull up the phone and look up the price online, and everyone knows that and every industry is trying to stay compatible with pricing or nobody would be buying anything from them... and I'm sure nobody wants to look like an idiot for giving unreasonable price. Now put all that all mambo jumbo aside, I wish you best of luck with your new home and I hope everything will go smooth and you end up with a well built home!