Our trees are grafted and only been in the ground for 5 months so it hasn't been possible to get an accurate cost of maintenance, but I think the highest cost will be labour which, in my case for the time being, is mostly free! (in-laws). More labour will be required in the future when it comes to keeping the undergrowth down and pruning. Once the trees are mature, say 7 to 8 years, I anticipate minimum of 10,000 baht average. Take a look at "lowbrow Thailand" on YouTube, There is a wealth of information there.