Create own apache web server on Arduino Uno... just like you can on a raspberry pi?
You can only make a very, very, very basic webserver, that won't be able to handle more than a few requests per second. 

You also need to add something like an ethernet shield, and probably an SD card reader. Which would make it about the same price as a Pi.

It's possible, but very limited, not practical in most cases, and not that much cheaper.