Is $3,600 to replace a 40 gallon gas water heater a fair price?

My water heater is over a decade old, and we have well water with a lot of sediment. I wanted to just go ahead and replace it, along with getting an alarm for the lift station/septic out back. I called the company we'd used in the past, but they got bought out and it seems like they increased their rates. They apply a discount if you sign up for their monthly club, which seems shady to me. I know prices are up everywhere but I was surprised with the numbers. I don't feel comfortable doing it myself, particularly when it comes to gas appliances. We have a pump out back for the drainage from our basement bathroom and washer that sends it up into the main sewer line. I currently have no way of knowing when the pump goes out, which it will at some point. The contractor didn't give us an itemized invoice but I'm going to get one. He wouldn't directly tell me the cost of the water heater when I asked.