This store is packed with kitchen cabinets. Some of the cheapest ones are just over $100 each. Huge selection of white, black, and gray ones. Most comes with free shipping.
Home depot is a one-stop-shop that wants to help their customers to build a home. At the Home Depot site, you’ll find everything from appliances, decor & furniture, to installation & services.
eBay is an online marketplace where you can sell and buy mostly anything. Both second-hand and brand new products.
The kitchen cabinets here seem to be a bit badly organized but you can do a search for kitchen cabinets and you'll find over 90,000 options. Its a bit hard for me to find out what are the cheapest ones for sale here, but there are some selling for about $25 each.