Is it possible to have different unit cost and price assigned for item per location?
Also, Is there any disadvantage if I enable the functionality of Change Log Set up with selected tables to record (i.e insertion, modification & deletion)?
Yes you can have different price for every location
I foresee there is no disadvantage in activating change log setup for tables but try to activate the change log for selected fields in tables rather than entire field list because it is unnecessary increase your DB size.
As well as periodically delete the change log entries this will keep you DB size in control.