Lowe's does not charge to cut lumber for the first 2 cuts.
If you need a few pieces of lumber cut or a sheet of plywood cut they will make a few cuts for free.
Then after the first few cuts if you need more lumber cut or more cuts done then they usually charge 50 cents per cut.
As long as you're buying the wood from them or the lumber from them Lowe's and even Home Depot will make a few cuts for free.
After that they have to charge because it takes up the employees time and the employees have to be paid for the job.
Cutting lumber is pretty easy too so if you can you should get a saw and then cut the lumber yourself if you're doing a lot of cuts of lumber.
The saw can pay for itself and you won't have to worry about having someone else do the cutting of the lumber for you.