If the item was listed as pick up only the seller must have had a reason. Maybe it is heavy or awkward for shipping? Maybe they don't have a vehicle to get to the post office? You said you asked eBay if seller would be prepared to ship but that is something you must ask the seller, eBay can't decide that.
I once had a buyer who wanted to pick up an item, I changed the listing to local pick up, they paid then messaged me I lived further than they thought and would I ship it instead. Because it was only a $15 item I couldn't absorb the shipping buy buyer said he would pay shipping how did it work. eBay advised me (back then) to cancel the order and re-list it with the shipping charge which is what I did.
You have to wait to hear back from the buyer, just in case they are currently unable to ship for some reason.
If you have a third party/wanted to send a courier, etc to pick up from them you would still have to be in touch with the seller so they could leave it outside for them, or make sure they are there. I don't know the rules about third party pick up but I would think if it is a shipping company it would make sense it would not be covered if seller has no control over which company or access to tracking, etc. However if the third party was a friend or family member picking up I would think it should still be okay (especially given seller wouldn't know what you look like anyways, could be you!) I had local pick up when someone sent their husband, no one would have a problem with that, it depends what you are thinking of doing.
Ideally, if it is within realms of doing yourself would be the best way, you don't say how far it is.
Since it was "well priced" there probably isn't a lot of room to absorb a shipping cost if not already included.
