Well, there is a point in making your own -- as a learning experience for us the less-experienced.
Messing around with a purchased one did not give me the sense that I know how things works. So, I made one from scratch using a virgin (no boot loader of any sort) 328p 28pin dip version and an FTDI TTL-USB conversion module. I boot-loader that 328 on breadboard to make the "Arduino" working, then later added the ISP header. After I got that thing working, I feel I have better understanding of things. I went on to make one for special purpose - a 4 channel volt meter using the MCU's 4 adc. No good use for it really, but good learning practice.
It is for sure cheaper to buy one of the shelf. I can get an Arduino NANO cheaper than I can buy the bare MCU. The FTDI TTL-USB module costs more than twice that of an Arduino NANO. The "4 channel volt meter" I made, well, I can get a NANO plus an ADS1115 modules off the shelf and have 4-channel 16bit ADC version at lower cost. The money I spend to made that two was for pure learning.
Apart from learning experience, I can agree that there is no other points in making your own unless you need a very specialized one like being able to operate it under extreme condition -- Hey, you can have the first home-made virgin Arduino (compatible) to receive it's boot-loader on the summit of Mount Everest...