There is NOTHING called UNLIMITED grafts hair transplant. For every individual, donor grafts are very much limited. Below facts might help you for better clarifty.
For FUT, maximum donor area for an average individual is 30 cms with + or - 2 cm variation i.e LENGTH and BREADTH can vary from 1 cm to max 1.5 cms depending on skin laxity in one single session. Very rarely it gets to 2 cms in breadth. This implies average AREA of FUT donor can range from 29 sq cms to maximum 48 sq cms. These are practical calculations.
Ideally every individual might have 100 grafts per sq cm and very rarely 120 grafts per sq cm. But practically its very very rare. You might NOT see a person with 120 grafts per sq cm even one in one lakh sample. Average individual has 60 to 80 grafts per sq cm (in practice).
This implies average a good donor can yield about 29X60 to max 45X80 i.e 1740 grafts to Max 3600 grafts with FUT. In cases where you can get 100 grafts per sq cm, we can extract MAX of about 4500 grafts using FUT. This is the MAX NUMBER OF GRAFTS anyone can extract from an individual with FUT. Its NOT UNLIMITED.
Example 1:
In normal cases, average density is 50 to 60 grafts per sq cm. They might yeild 1500 to 2250 grafts. In this case unlimited grafts equals to 2250 grafts only.
Example 2
In few cases where average density is 40 grafts per sq cm, they might yeild about 1200 to 1800 grafts max with FUT. In such case unlimited grafts are equal to 1800 grafts only.
By Combining above FUT with COMBI techniques i.e FUT + FUE done on same day, we can extract another 1000 to 1500 grafts extra on top of above MAX GRAFTS.
BUT, if you count grafts as single follicles i.e single hair strands, then above values double. The new range will be (3600 grafts) 7200 single follicles to (4500 grafts) 9000 single follicles (But NOT standard grafts). You can notice this small trick in mathematics below those advertisements in very small invisible fonds with (*) mark while many clinics advertise 10,000 follicles in one single session.