Every domain is for sale, it does not matter if the cost is $1 or $1,000,000. Everybody has their price at some point.
When someone steadfastedly refuses to sell and instead only offers to lease that is your cue to look very closely at the small print, all too often it will be one sided in the favour of the person writing it up; ie they will lease it to you for an exorbitant fee each monthly or yearly cycle and you do all the work and then at some future point they simply take it.
With any propert even if you are not interested in buying you always make sure you have the option to buy at some point in time, this gives you at least some kind of way to take advantage of the work you put into it. If you renovate a dilapidated shack in the middle of nowhere and get it somehow making money if you do not have a buyers clause the owner still holds full rights and can evict you at any point in time. (Though you need to ask professional counsel on this)
Thats just my thought, someone who will not even consider letting you buy the property you have spent time on is probably not someone you want to be doing business with.