So far you have gotten lots of advice based upon your original posts. We have not seen pictures of the tortoises. I kind of wonder why you have not posted pics for us to see since two people other than me have asked you to do so. Posting the pics, of the actual animals you sold, could only help us answer your question more intelligently.
Without the pics, all I can say is I would offer some sort of a refund. This sort of happened to me last year but it was that a kingsnake I sold supposedly died after two weeks of care on the buyer's part, or so the buyer claimed. He never sent me the snake back (on ice) and never sent me pics. I sent a refund minus shipping, it was not a lot so I took the hit. I doubt that the snake died. Another fellow bought a hognose from me that I advertised as a severe problem feeder (fed once or twice only and this was in my ad). It died in a few weeks. I offered a refund, he did not take it. I happened to see him at a recent snake show and gave him a free snake hook and offered a baby black rat snake - all I had in my inventory as far as snakes went - he declined again. Normally I would not sell problem feeders. I only sold the problem feeder because I had volunteered to fly as a Federal Air Marshal until the FAA (now TSA) hired enough people to do the job (I am a fed agent). I had to make the sales fast as I knew I would not be around a lot to care for lots of baby snakes.
Now I realize my situation is different from yours; however I got lots of advice both ways just like you are getting from some of the same people who are giving it to you. I figured that in order to protect my future dealings online it was best to at least offer a refund.
The guy you are dealing with may be a jerk, and may not be one. Whatever he is, it is probably best to offer a refund and he pays return shipping. HE SHIPS FIRST (He ships first, he ships first, he ships first, he ships first, he ships first {kind of important at least in my mind}). You receive, by overnight shipping, apparently healthy tortoises (and make sure these are the same ones you shipped him - give them a good look over comparing them to the pics you took) , and then you refund the full purchase price minus shipping. That way if your customer ever decided to bad mouth you on forums you can defend yourself with very commendable actions on your part. By the way, those same actions would also probably hold up in court if he tries to bring you to small claims court for the shipping fees or whatever - some people are that dastardly you know!
Remember if he sends them back , and you give a refund, you can always sell them again if they are in as good a condition as you claimed (and I am not doubting you - I don't know you enough to do that). Good luck
Best regards,
Glenn Bartley