Pricing is a big consideration in the choice between new and used, of course, but you really need to add up all the costs when you are looking at any tub. If I show you a new tub on my showroom floor, I can easily tell you a finished price. In most cases I simply add a lift, tax and we're done. some models don't come with Ozone, but that's easy to add in to the price as well, and then install it on delivery. I can even add in the electrical work if needed. My point is: you have a complete price before you write the check.
But when you are looking at a used tub from a private party, it is easy to focus on the asking price and stop. Sometimes folks get tubs
free and then come to me complaining of how much I want to charge them to move it, the price of covers, filters, etc. Get as many prices as you can up front - you will hardly ever end up near the price of a new tub (at least not a major brand) but then, you're not going to get the equal to a new tub for pennies. All those nice shiny new things cost no matter who you are getting them from. Few people replace the cover just before they give a spa away, so keep in mind you will need to spend a bit more to get the thing running in your backyard.
People expect more from a dealer than a private party, and it costs more. When I go through a used tub I put in new Moto Massage assemblies, new filters, a new heater unless I can verify it's less than a couple of years old, new headrest pillows, new cover and if the lift has air (gas) springs, I usually put those on new as well. I
always put a new circ pump in, and I may update the heater relay board just to be sure there are NO problems with anything on the tub for a good long time. I mostly only sell HotSpring tubs used. I do sometimes get other brand tubs, but it has to be in amazingly good shape - and usually a brand I have sold in the past so I have some knowledge of what to look for.
That gives my customer peace of mind, but it costs money!! By time I have done all of the above, I have put an easy thousand dollars worth of parts into the tub. The labor is minimal - I can put the tub on the forks of my lift and have the motor compartment scrubbed clean and refitted in under an hour. I don't generally sell tubs with wood siding if I can avoid it - but having said that it dawns on me that I have three tubs with wood siding in stock! It happens...
HTH