I want to buy new speakers for 50,000 and see it used for 30,000, what should I do?

@OP - your post does not raise a concern that very nice speakers are too expensive. With very rare exceptions, consumer goods depreciate. Not nice speakers depreciate and very nice speakers depreciate. Actually, very nice speakers depreciate less.  Speakers have a long service life so their depreciation can be amortised over many years. Anyway, that has to be set against the pleasure of listening them, and what price does one put on that.

I don’t believe you are crazy. 
 

I have a good relationship with a local stereo shop - and I go there for all my purchases (new or used). They deliver, set-up and stand by the product. On demos I get the warranty and in some cases manufacturers (e.g., Wilson Audio) have certified used programs. 
 

Good luck!

I would buy the used speakers if and only if I could see/hear/touch them beforehand.

I've never considered the fact that I have a wife unfortunate or unlucky. Guess it all comes down to choices, eh?

If you’re spending that much, go inspect in person, listen, heck even tote your amp and cables. You can afford the flight, a first class hotel, steak dinner with a bottle of Lafite to celebrate purchase with what you’re saving! Unless you hate them, then you’re saving more.

My personal experience is this: I have purchased speakers used that I could not afford new. In my case I was happy with the used ones and the 11K I saved- which went into a good DAC. I was happy with the allocation, Additionally the mfg. warranty transferred. No issues arose and I use them to this day. 

I have also purchased new. (times change, wealth changes, etc.) and I was not especially bothered or impressed by "brand new" although the speakers were and still are impressive. 

It's totally an individual thing. To me my AMG 63 was a steal 18 mos. old. I saved 35K. It felt new to me. So did the used speakers. Because I'm a number nerd I consider how much 25K or 35K is worth in a decent investment multiplied by 20 or 30 years, As Warren Buffett says "It soon appears indefensible".  I'm 62. That wealth will get used either by me or my heirs. That's defensible. Meanwhile I have luxury for "relatively cheap".