Welcome and congrats on finding a "mint" condition 1500. We all want the best bang for our dollar; however, where you live and what is available most often dictates what you pay for things. I know because living on Vancouver Island is a very small motorcycle market, and when a bike comes on the market that you want and there are not a lot of them, you can pay a premium for it.
It is a used bike and as such, warranty is generally 30/30. 30 feet or 30 seconds; however, with the 1500 it is quite bullet proof. Was concerned about carbs, and maintenance when I bought mine with 155,000 Kms on it, but it has proven to be a very reliable touring and daily rider. I did the usual maintenance, some accessory upgrades for myself - had no other reason to do, and upgraded the suspension. This has kept the cost down.
You may be able to find one that is less expensive to start, but with all older used bikes you never know what is under the hood until you get it home. You can easily spend $2K on these bikes with tires, brake parts, fluid changes, suspension bits, and such.
Does the bike have any aftermarket electrical additions, if not great, if so, ask to see how these were installed. Wiring issues can be a challenge.
If this is the bike you want, and it has been cared for as you say, negotiate the price, but I'd speculate that this gentleman is looking at the $6500.00 USD range. Any less he will probably say no thank you. If it is what you want, in your price range, and you can buy and ride, go for it. You can always shop around, spend a lot of time and energy doing so, and return to the same starting point, happens all the time. You can shop around and return, and it's gone, damn let that one get away.
Long rant, but the bottom line is, do you like the bike, do you have a warm and fuzzy feeling that all should be well, and it fits your budget, ask what his bottom line is - he'll tell you, buy and ride. Remember it is a 26 year old bike.