That looks awesome! From comparing prices online, I'd say a good competitive price would be $125-$150 for something that size, although you could probably get more if you weren't in a huge hurry to sell them. The one thing you want to keep in mind with selling to pet stores is that they will usually only pay about half of what they can sell it for, so if they can sell them for $200 you will probably only get about $100 for it which kind of sucks. I used to work for a small pet shop and we would buy cat trees from a local guy that made them and I'm sure he would of gotten a lot more for them if he just sold them himself. Also, the flea market could be a good way to go, just keep in mind that, atleast around here, everyone at the markets wants everything for less so you may want to price them higher than what you actually want for them because everyone is going to try and haggle you down. I used to help my brother sell stuff at the flea market and he would have things priced for less than a quarter of what they normally cost and people still acted like he was charging to much! It was really quite frustrating. You're selling something, brand new, for $20 that would normally cost $100 and they still want to try and offer you $10! Cheap people....