Arduino would not typically be used in Industry or End Products. Anything requiring mass production would use a custom board that could be made under a manufacturer's control with a parts list they could control and with software written for that application. Arduino could be used to prototype the design as a proof of concept, but the production version would only carry the chip and crystal forward; the rest of the board would be shrunk down, including the processor (going to surface mount for quicker automated assembly), unused parts would be deleted, other parts might be added to support the end product.
An example would be this programmer. The '328P processor and crystal are in the lower left corner. The Arduino headers are gone. A rotary encoder is added, a display and drivers are added, a SD card and voltage level shifters are added, some control buttons and status LEDs are added, and 2 connectors to connect to the card being programmed are added.
An interesting place Arduino has been used is my Fencing Scoring Machine. If one looks close, two ProMini's can be seen.
One is used to detect when an attack has successfully scored, the other controls the lights and buzzer (and talks to two remote light boxes. A 3rd Promini is used in the Remote Control.
In both examples, the end item did not need to connect to a PC, so a Promini was used as the USB/Serial adapter and other features (connectors, auto power source switching, USB and power connector) of an Uno were not needed.
The Arduino MEGA has memory (256k program flash and 8k ram) and performance (16Mhz/8bit) that are "roughly similar" to the original Apple Macintosh. (64k rom, 128k program space in RAM, 8Mhz/16/32bit executions)
Similarly, the uno compares to the somewhat older cp/m systems in memory size, but runs faster.