2014 ford focus
The cheapest would be a locksmith but it may not be the best, a lot of them don't have the equipment to setup the chip. The best place would be of course the dealer but that is not the cheapest, but they have the equipment to set it all up too make sure it functions properly.
Search Ford Focus Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Ford Focus Experts