Nowhere does the maxim "you get what you pay for" apply more than to hardwood flooring industry. There are many differences you can see with hardwood flooring on the surface and there are many that you can not see until it's too late.
Cheap Scraping
Cheaper hardwood flooring is machine scraped but often sold as machine scraped, however over time you will start to notice that the machine scraping leaves repetitive patterns. Do you want to live with wood that looks fake, especially when it's in a larger area.
Finishes
Quality hardwood floor has a finish that helps bring out the inner beauty and enhance the wood pattern. Cheaper wood floors use finishes to cover up imperfections. Look for inconsistencies in the wood finishes such as discoloration and variations in surface depth.
Precision Milling
If your flooring is manufactured using high quality machines, the tolerance between the tongue and groves in the planks is superior, this eliminate creaking in the floor. This may not be apparent at first, but after weeks or even years, the gaps increase due to wear and environmental changes. Furthermore higher quality milling results in consistency in that height, weight, length and edges that will be obvious after install.
Long and Wide Planks
The cheaper wood flooring products will limit you to shorter and narrower planks. Smaller planks allow the manufacturer to use less quality wood. In larger and smaller rooms long and wide planks will be aesthetically pleasing.