How much would a microdermal neck piercing hurt?

The pain honestly isn't something you should worry too much about as it fairly fast (little slower than piercings but still over in less than a minute) and I have found them to be far, far less painful than getting any piercing excluding ear lobes.

Pros and cons with microdermals are; pros they are less painful than piercings, they are more permenant, less likely to reject and give the singular look of just one ball. Cons are they take alot of healing time and can be quite time consuming and problematic in that they catch easily and often have to be taped down at night to prevent them catching in your sleep and they are very suseptible to infection especially when they are in highly used areas like your hand and/or wrist.

I have three microdermals myself, two on my forehead and one on my wrist, I have seen and known many people to have them in various areas and most have told me similar to my experiences. If you are willing to look after it well and deal with potential infection and catching then go for it.

Hope this helps.