Hot tubs are expensive. Even free craigslist jobs come with tremendous costs:

• Moving the (very heavy) hot tub
• Installing the (very heavy) hot tub somewhere you can put a bunch of heavy water in it
• Repairing the hot tub
• Getting a heater for the hot tub (free on craigslist rarely comes with a functional heater)
• Getting a cover for the hot tub (covers are VERY valuable [more later] and therefore pretty expensive, and therefore often sell without the actual tub)
• Running power to the hot tub (240V, high current)

Even if you can get your buddy, your buddy's truck, and 4 other friends to help you heave the thing around, a big foam-packed plastic tub is still a long way off from a functional spa, even if it's watertight. 

Ballpark, assuming you don't already have 240V in the perfect spot on a patio, a hot tub will run you $5-10k before you even turn it on. Maybe $4k if you get a "free" tub, and maybe only $2k if your buddy with the truck is also an electrician.

Enter the inflatable spa.

I can say with confidence - if you're looking at this and thinking, "hmm, that's a good idea!" - you're right. Go get one. On Prime Day you might even be able to get one of those 6 person models for $350. To be clear: yes, it fits 6 people, if you're all close friends. It fits 4 comfortably. 3 if you don't like each other. It is worth every penny.

But then, $350 and $3500 are pretty far apart, and there are good reasons. So maybe read on first.

The REAL cost of a $350 Hot Tub

Ok, so the CAPITAL cost is much cheaper. But that's not the whole picture. Here's where the hot tub owner spends money:

• Capital (purchase) $$$
• Consumables (chemicals)
• Personal effort
• Accessories
• Energy $$$

Personal effort - well, you're a hacker, so you're probably not the type to pay someone to make the problem go away. Ignore this.

Consumables - these are pretty cheap, especially for such a small volume of water. As a point of reference, I've spent about $60 or 80 on chemicals since the start of this, and I'm in no danger of running out of anything soon. It's more like, a $10 bottle of chlorine that'll last you a year, a $18 bag of Alkalinity Up that you'll never finish, etc.

Accessories - get what you want, duh. We always kinda go nuts on projects, don't we? I recommend a hand-held pool skimmer, but otherwise, budget appropriately.

Capital - This is the single biggest cost, and with the inflatable tub, we've knocked it WAY down.

Energy - This is the second biggest cost, and knocking this down is basically the whole focus of this project.