Expensive eGPU box or cheap PCIe riser on a laptop ?

I want ask experts here :
I wanted to install an external graphic card on my laptop , when i searched for the hardware to do that , I found few with comparatively expensive price tags .
One of my friends came up with an idea that ,"if miners can use PCIe riser to install gpu out of the casing then we can also use these riser for an external gpu for laptop" .
Is it possible , should I buy one ?