Toothing in to an existing floor cost from $35 to $55 per square foot depending how much work needs to be done, When material is not provided, expect to pay the higher cost.
This Process is sometimes referred to as lacing in, Inner Weaving, Tie In to an existing floor. It take skill, and practice.
On occasion adding on wood flooring to existing need to have the lace in as a starting point to install you floor since the existing floor will dictate the line of starting in the new area. In some cases its just easier to tear out wood, if its a small area . Every situation is unique, that is where an experienced flooring craftsman can do the most expeditious and cost effective assessment.