I bought the cord to save me effort and to reduce risk. With the cord, I don't have to worry about shutting off the power and screwing around inside of the receptacle box (which is behind either my dryer or my range). It was under $25 - no biggie. Plus, now I have a spare dryer cable...yeah, I'm going with the dryer outlet. I had to get adapters for the water lines because they are NPT and I'd like to just hook it up to the washing machine line (you're good suggestion) which is hose thread. Plus, I can hook up one of my existing garden hoses and route the water to the kitchen sink or outside.
I'm just about $50 into it after going to Home Depot just now. It's a project, so I don't feel bad about the money. I've learned things, too. First, I learned that washing machine hoses have the same threads as garden hoses.
I also researched electrical systems and learned some good stuff about how houses are wired. I also learned the difference between neutral and ground. Yeah, I could have researched that stuff on my own, but I wouldn't have had a reason to without this project.
I almost surely get to keep the heater. The company can ask for the unit back, but in about 6.5 years in the program, that's only happened to me once...kind of. It was a Moen faucet design that arrived damaged twice, so they asked for both of them back to inspect them. They then shipped me another one with new packaging, so I still got it.
They offered me the heater, I accepted it, and it's all with the understanding that I'll use and review it. So, I'm going to use it. I'm not going to do a full install, for a couple of reasons. First, I'm pretty sure that it would be $250+ just for the raw materials (breakers, cables, boxes). I'd be shocked if I could get that all installed for under $250 in labor. So, $500+ to install it - and I don't want to replace my gas water heater. If/when it fails, then I certainly might consider installing this because then the install will cost about what a new water heater would cost.