Battery socket selection
A quick eyeball of coin cell holders at Mouser shows the cheap ones being the ones that are only a holddown and contact for one side - just a piece of stamped metal.  The second contact is a pad on your PCB.  You have to have space adjacent to the battery holder to lie the battery down and slide it into the holder.

The more expensive ones tend to be insulated and have both contacts built into an insulated shell with a hold down for the battery.  You can insert the battery into these from the top - they don't need as much free space around them.