An extended warranty thru" a Land Rover dealership would cost you between $2.5K -$6k, based on mileage and years of coverage you choose. Naturally, the price is somewhat negotiable, as the dealers would mark it up and try to make profit on it. I was considering it, but then realized that my GEICO insurance policy covers mechanical breakdown (with a modest deductible per repair)
I am sure there are some third party warranties that are cheaper, but one should exercise caution with those and discuss it with an LR dealership service dept to make absolutely sure that it is going to be accepted, no surprises.
With GEICO, I am pretty confident, as it is a reputable company, no hustle at all (but cost extra)