We entertained a property on a land lease a couple of years ago, but in the end passed on the opportunity as the land-lease termination date was not far enough out {2-3 generations by our determination) and the lease itself had no provision for renewal or purchase. Otherwise, the lease rate was excellent (<$100 / month) and building price was suitably depressed due to the lease.
In your instance, the lease end is far enough away that you should still be able to sell the property in 10 or 20 years. I would also look at the terms of the land lease to see if it provides a favoured clause {and terms} for renewal or purchase at the end of lease. I would also look at the lease rate formula to see how the lease amount will increase in the future. You state the HOA fees are approximately double the median rate in the neighbourhood; is it safe to assume that difference is the land lease? If so, $200 - $250/mnth in land lease adds considerable overhead.
How are the property taxes handled? Does the building pay them, or does the landholder assume a portion?
In the end, my advice would be to first confirm the property meets the same rigorous evaluation you would apply to any property and, second, to verify the land lease provides you with a viable exit strategy.