Disclaimer: This is not a knock against Kirby Vacuum Cleaners. They probably make the best vacuum cleaner in the world, but if you've bought one or your 80 year old mother has bought one and the next morning you decide that a $1945 vacuum was not a good purchase there is something you can do.
Also I not an attorney and am not giving legal advice. I'm passing along my experience and you should check the laws of your state before you act.
I can only speak of the laws of the state of Texas since that's where I live and where I have my experience. Your state or country may vary. Check the laws of returning/buyers remorse before you buy if you can and as soon as you can if you've already bought.
Step 1: Before the buy.
If you've not bought yet then do some research before making that purchase. If you plan on buying something to pass down to your children or run a cleaning service maybe you need to spend $2000 on a vacuum cleaner.
But if there are less expensive models, brands or products that will meet your needs then maybe you should make your purchase differently.
Look at reviews of the different products that you are interested in. A few bad reviews don't mean the product is bad or their service is bad but if you find hundreds or thousands of bad reviews then you should probably look elsewhere.
If you don't know how to do a search go here and ask a question. You can even ask for an opinion there if you like.
If you find that the high priced item is what you really need then by all means buy that one.