Wow isoMorphic that got political for no reason. First of all I am not sure how versed in economics you are, but your sentiment is skewed and has no merit or economic data to back it up. I will not even get into the global economic argument.
Whether one buys locally or not, you are supporting US business. If kept in the US, the tax situation is the same. The only difference is the municipality you do not chose does not collect taxes (if it does) and the local business does not get the sale.
Every company starts off as a small company somewhere. Some choose to grow and the economies of scale benefits them (B&H, Adorama, Cameta, Amazaon, Starbucks, etc). Some choose to grow and fail to innovate (Ritz, Borders, Blockbuster, etc), and some simply choose not to grow and do their best with the status quo (most local mom and pop stores).
You cannot fault a company that grows and succeeds and as a result of their scale can offer lower rates. Companies with larger scale can sell it cheaper because they sell more inventory. The initial purchase of the product by the vendor is generally the same from vendor to vendor, or sometimes discounted to the larger purchaser. That will always be the case. You take care of the people who take care of you. Happens from vendor to distributor and happens from distributor to customer. The customers that are more loyal and do more business get more perks. This same principal applies to local shops. The local shops that do not grow and stick to a brick and mortal presence opting not to innovate largely understands the consequences and offer great service and a competitive offering. The camera industry and other high overhead industries are going to and are starting to adapt as time will show certain business models are not sustainable and opening a store with huge overhead costs and little to no inventory as a result cannot work in the present age. Should Blockbuster be upset because they chose not innovate, get online fast enough, or handcuff their distributors, and open monstrous stores with unsustainable square footage? Certain businesses will fail with innovation. This has been happening for thousands of years and mom and pop camera shops are certainly at that cross roads now.
That is how the business side now let's talk about the individual impact.
The person willing to buy a product has a home, bills, cars, etc. If they save $200 on a purchase, that same person, will either save that money, reduce their debt, or more likely spend it, contributing further to the GDP as more products will be sold than had they overspent on one. Either way the person who chose to save will generally have more money, buy more inventory, and help more businesses than the person who does no research and buys a product that costs x% higher than they could have got elsewhere.
Example, Chrysler sells CarX at various dealers. Invoice price is the same per dealer. Consumer opts to go the the dealer 50 miles away because they save 2k off MSRP over their local dealer. We can all agree this transaction happens hundreds, if not thousands of times a day in the US. Chrysler counts that sale as one unit sold, regardless, grosses up into the consumer spending index and consumption portion of GDP. That same person either could not have afforded to spend the 2K locally to the local dealer was not going to get the sale either way, or they are going to choose to do something else with the 2K, pay down mortgage, invest/save, or spend it on a 7D, then repeat cycle.
Assuming local population growth is positive in the neighborhoods, capitalism takes care of the rest. The business that can compete will, those that can't or refuse to will close shop and something else will take it's place and the business that replaces will be something that hopefully will be better adapted to the business environment it is entering,