A hot tub is a long term investment. Pay $5K for a cheap one and replace it in 5 years or pay $10K for a good one and have it for 10-20 years. You can find a good used tub if you are very diligent but you could be buying someone else's nightmare. Most I saw in my local market were in poor shape, non functional and really old. You really need to see a used tub filled, heated and fully functioning. Also remember, no warranties on used even if still within the manufacturers original warranty period as warranties are only for the original purchaser.
I have been through this. My first tub was a 4 person (really 2 usable at a time), 110V at about $1.5K about 20 years ago. I was uneducated and bought strictly on price and it was really an impulse buy from a low end manufacturer. While we used it, it had a lot of shortcomings. We left it when we sold the house. This time, I originally thought I could do it for $5K and though research found the only $5k 5-6 person tub in my size constraints was again a low end tub from a less than stellar manufacturer, had poor dealer support and contracted out to any spa tech that would handle warranty claims. I did a lot of dealer visits ( which was difficult during covid), lots of reading and chose my new tub based on manufacturer quality, dealer support, customer feedback on the manufacturer, my feelings on how the dealer visit went and dealer in house service. I ended up choosing an Artesian Island series spa and couldn't be happier. I ended up at $9.5K with steps, cover, lifter, hand rail, startup chemicals and a years worth of Frog cartridges. So far, the dealer has been extremely responsive to questions and the service tech called me back within minutes when I called with a potential issue that was easily remedied with a 5 minute walk thru on bleeding an air bound pump. At my age, I really don't want to buy a replacement in 5 years.
Buy once, cry once.