Yep, about $100. Same price as a 50g or a 55g for me actually. I do think if you are planting the tank though the 40g long is a great tank to work with.
I don't know where you live , but I just got a 75 for $109 from That Fish Place. Not sure about a 40, but I wouldn't imagine it would be more that that.
walmart has there aquaculture tanks for bout 140 for the kit. If I knew that the tank was compatable with the tops I want I would buy it from them. I just wish you could find reasonable prices on tanks by themselves. Without the hunting for used.