Does this sound like a reasonable price to extend a lease?

[thepeopleversuswork]

I've applied to extend my lease from its current 85 years to 125 years. I've been quoted just under sixteen grand by the freeholder.

I know each contract is different and subject to its own vagaries etc but this sounds like a total rip-off to me. I know anecdotally of people who have paid a fraction of this for multi hundred year lease extensions.

Any advice or just a sense check would be much appreciated here.

We recently paid £6k plus the freeholders legal fees which were £700 to extend the lease on a 3 bed split level maisonette in SW London. We had 92 years remaining on the lease.

So much ignorance on here! And your freeholder is playing on your lack of understanding of lease extensions.
You are being ripped off!
As your lease is above 80 years it should not cost anything like this.
Please read up about lease extensions.
There are two ways of extending your lease - one way is formal, the other is informal. Do not go the informal way - it could cost you dearly - not just the cost of the informal extension - but because many unscrupulous freeholders have a habit of sneaking new, unfavourable terms into the lease e.g. onerous new ground rent terms which you may not notice and which will seriously devalue your property.
There is a formula for working out the cost based on how long you have left on your lease (under 80 years is the problem zone!) and how much your ground rent is and if it's a rising ground rent..
Going the formal (statutory) route will cost more in solicitor and professional fees as you have to pay both sides though the freeholder's fees have to be deemed reasonable. Going the statutory route will also add 90 years to your existing lease.
Make sure you employ a specialist lease solicitor to ensure they can spot any potential nasty clauses that your freeholder may try to sneak in to your lease whilst extending.
Join the National Leasehold Campaign Facebook group for any advice and/or established, recommended Leasehold specialists.

Make sure you employ a specialist lease solicitor to ensure they can spot any potential nasty clauses that your freeholder may try to sneak in to your lease whilst extending.
Agree with this. I presume that you didn't do the conveyancing yourself when you bought the property, that you used a solicitor to make sure that the legals were watertight . Use the same logic again here - it's going to cost thousands and thousands of pounds so you want to make sure that you are not being conned. The legal fees are an investment, not an expense.

There are some proposed changes to leasehold law, you might want to talk to the solicitor about them and the timings involved. Example article here

The value of the property is irrelevant as there are more than 80 years on the lease, could be 100k or 20m, lease extension cost will be the same

What is the value of the flat and what is the ground rent and its review pattern ?

Without this information, it is impossible to comment

If the ground rent was say £250 per annum and the flat was

@Alexalee

The value of the property is irrelevant as there are more than 80 years on the lease, could be 100k or 20m, lease extension cost will be the same

Absolute rubbish.

The value of the reversion forms part of the premium and is discounted at 5% (Sportelli is the case)

In microsoft excel put in the following

=round(X/round(1.05^y,2),2)

where X = value of the property and Y number of years left

That will give your the value of the reversion

You then need to add the capitalized value of the ground rent