If I were selling a guitar, I'd be thrilled to have the buyer meet me somewhere and personally take delivery. Shipping is a huge hassle that also includes the risk of damage, which the seller has to deal with. That's all avoided with hand delivery. Also, a buyer might look at a shipped item and deem it not to be as described, wanting to negate the transaction. If that happens with a hand delivery, it's far less inconvenient to the seller than getting an angry email and being told that the instrument is being returned and a refund is demanded. Face-to-face, both parties can determine if they're satisfied with relatively little disruption or drama. The buyer, of course, also has the reassurance that the goods payed for will actually be delivered. So, to my mind, any minimal inconvenience of a local hand delivery is more than offset by the inconvenience and risk that the seller is avoiding as a result of the local hand delivery. I would not be pleased if a seller wanted to charge me for eliminating that inconvenience and risk to him/her.
I did a swap recently that involved driving a couple of hours to a place that was about twice the distance for me as it was for the other party (but was reasonably convenient for both of us). We met, grabbed a bite, chatted, looked over each others' instruments, made the swap, and left happy. I picked up lunch and he left the tip. I was happy to pop for lunch but had he asked for $10 for his inconvenience, I would have been sorely displeased, as I had traveled farther. That request would have made a pleasant transaction an irritating one.
Everyone does things their own way, of course, but it's hard for me to see how getting another $10 would be worth turning a transaction from pleasant to ugly (or, in this case, into a non-transaction). I think the seller was just plain silly to ask for the $10.
I remember another transaction in which I was buying an instrument and the seller was about to leave the country on vacation. He wasn't sure about shipping but thought it would run around $35 and that he'd send me a precise figure when he could. I added $50 to the agreed-to price, Fed-Exed him a check overnight, said that I thought the money for the instrument would be handy for him and his wife to have for the vacation, and told him that if the actual price was less, for him and his wife to have a beer on me when they got to Ireland (their destination). This was about a $1500 transaction and $15 one way or the other wasn't a big deal. So, the next day I got an email, thanking me for my generosity, and telling me that he had sent it overnight (which was not the original plan) as a way of returning my kindness. That cost him at least $15 more than I'd sent him but he insisted that the difference was on him. So here was an instance of my extending a small concession and receiving another probably of greater value. We ended the transaction both feeling really good about it and kept in touch thereafter. I love it when stuff like that happens. It actually saved me some money in that case, but I would've been just as happy about the outcome either way.
I'm perfectly willing to haggle about a selling price to get a good deal. But once that price has been settled, I want the interaction between me and the other party to be as amicable as possible. I try to make payment really quickly and I find that most sellers appreciate that and are also speedy to ship to me. A face-to-face transaction should be the perfect opportunity for this kind of mutual courtesy.
