A good question, totally legit. Why can't we just get a photo taken on a smart phone? After all, latest smart phones have high resolution cameras (often higher than professional cameras), right? Those photos cost nothing, on the other hand we have to pay a professional for photos, right? We can, but that's the wrong question to ask.
The question we need to ask is this:
"Can I confidently make these photos LinkedIn profile pictures? "
"Am I comfortable or even proud to share these photos with others?"
Comfortable? perhaps, but proud? no!
If you have a photo taken on a smart phone and another taken by a professional, which one would you share with confidence? The one shot by a professional, obviously. There lies the answer to the question which is, "Is it worth paying to get a professional portrait or a headshot done?" - yes! it is totally worth it!!
What you get in return for what you pay for a headshot or a portrait done by a professional is confidence about your self image, your brand. You will proudly, confidently set these as your profile pics. I would say anything that makes you feel comfortable and proud is totally worth it. It is what you feel inside that matters - well that's all that matters, rest doesn't. What do you say?