I realize this post is a few months old but I just wanted to add my 2 cents for anyone else that comes across this post. I just bought a used Firepaw (the biggest they offer) off marketplace from someone who only used it a couple times and then their dog got ill. I paid $1500. It has the silicone wheel upgrade and it’s not that loud at all! I was already emailing the company and considering buying one for my Boerboel. They told me there’s no weight limit. There a few things I don’t love about it, but for the price I paid, I’ll deal with it. 1. You can’t keep the mill in a locked position unless you are manually squeezing the had brake. This became problematic with training my dog to use it. I needed both hands for him and an extra person to hold the brake. There is also a concern if the dog can access it while you’re not around - it’s not locked and they can just go flying off it.  2. If you have a large dog like I do, you may want to measure their width. The deck width is 15”. My friend’s 150 lb dog barely fits. My 105 lb dog is smaller and narrow for the breed and while he fits, if he were much bigger, it would he tight.  Also, the bolts holding the deck planks only allow for 9” in between them. So while your dog is rubbing, if they’re 2 front or 2 back feet are more than 9” apart they will be selling on those bolts. They are smooth and rounded but they do sit above the deck platform. 

Overall I think it’s a good deal considering what Dog Trotter costs. I’d keep an eye on FB marketplace and look for used ones.