A single point repair costs less than a full lining because it uses far less liner and resin. Several point repairs on one line can cost as much as a full liner and still leave aging pipe between them. The camera footage shows which option costs less over the life of the line.
The detail
The comparison only works if you count the whole line rather than the current defect.
One defect, sound pipe elsewhere: point repair wins clearly. You are paying to fix what is broken.
Multiple defects, or a line that is uniformly old: the maths flips. Three point repairs approach the cost of a full liner, and you still have original pipe between them, with the same age and the same joints that failed everywhere else.
The age question. On a pre-1980 cast iron line, a point repair fixes the section that failed first. It does not change the condition of the rest, and the rest is the same age. That is worth knowing before you choose, not after the second repair.
We would rather show you the footage and let you decide than quote the cheaper job and be back in two years.
Related: cast iron plumbing