What has been your costliest mistake in this hobby?


For example :I recently learned a hard lesson- I accidentally ran voltage thru my $3000 MC cartridge (kiseki purple heart).  I have a TT with 5 prong connector and a phono cable with a 5 prong connector.  I accidentally swapped where they plugged into and ran electric thru the tonearm into the cartridge.  It was a stupid - not thinking- hasty mistake. When I corrected the problem the cartridge was fried.  An avalanche of four letter words followed!

So what has been your biggest and/or costliest mistake?
polkalover
The costliest part of this audio journey for me is my inability to sell gear.
I sure I'm not the only one afflicted with this disease. The upside is that I find Easter Eggs when I'm hunting for something in the house that is unrelated.  Recently found three Hafler amps in a closet and a GAS amp (remember those?) in the attic. 
The only piece I ever sold was a Teac A-3340S 4 channel RTR, because I had two of them!
 
Upon leaving college I "sold" a pair of B&O speakers to my room mate. They were very good at the time mid-70s.........costly yes, because I never got paid for them.   
Biggest mistake I made was buying a pair of highly regarded floorstanding speakers which got many great reviews without ever hearing them first.  They sounded God-awful so naturally it couldn’t be the speakers.  I replaced every component and wire in the system at a tremendous cost and after many tens of thousands of dollars, the system still sounded horrible.   After many sleepless nights, I sold the highly regarded speakers and started over.   Lesson learned.  I will never buy something like speakers without hearing them first.  That mistake cost me upwards of 40K. 
A well-known vintage audio dealer was selling tradeins on Ebay. I had purchased used equipment from them before and they were about two hours away, so anything I bought I could pick up personally rather than risk having it shipped. When I first bought equipment from them, the store’s owner took me to the back room and showed the unit on the test bench, which led me to assume that they do their own repair in house. So, after perusing their Ebay listings, I bought a Sansui AU-717 that had been owned by one of their regular cuctomers, who was its first owner.

I called the vintage audio dealer and reached the guy who handled their Ebay sales. I paid a modest amount to have the tech--who I later learned was an outside contractor--look it over and replace anything that needed it. That was my first mistake: not being clear about what I wanted done. Did I want a full restoration, or just "fix what’s broken" when, according to the listing, everything supposedly worked fine?

I was shown the Sansui powered up. Second mistake: I didn’t take the time to ask them to pop the hood and let me look inside. I took it home and installed it in the system (in retrospect, another mistake). On the third day it went into protection and stayed there.
At that point I should have taken it back to the seller. But, reluctant to make the drive and thinking that I needed to find a reliable repair shop closer to home, I took the crippled Sansui to a vintage audio dealer about half an hour away. That was my third mistake. Even he questioned why I didn’t take it back. When he showed me the unit powered up and working a few days later, he talked as if he did the work himself. Again, the charges were quite reasonable.

The Sansui failed again about a day later. I had intended all along to have it completely restored if I liked how it sounded. Trolling Ebay, I found a Sansui restorer there whose listing was persuasive. Now, before the ritual denunciations of Ebay start, I’ll state that I have bought and sold audio equipment on Ebay for close to a decade and, with few exceptions, had positive experiences. I emailed the restorer and asked whether he would be interested in repairing and restoring my Sansui AU-717. I would have to ship it most of the way across the country.Before he replied, however, I found that he had for sale a completely restored AU-717. I pulled the trigger on it. That purchase was a righteous one. The unit is still in my system and performs wonderfully.

He expressed interest in the crippled AU-717. We agreed on a price and I sent it to him. I enclosed copies of all the paperwork and emails describing the unit’s condition and the various repairs paid for. After he received it, he emailed me to advise that none of the work that I had paid for was done. Items that supposedly were replaced were not replaced. I had been scammed--twice. Inside, the unit was very rusty, almost as if it had been in a flood. It was so bad that he complained that he could not use it as the basis of a rebuild project, and we agreed on an adjusted price.
When I totaled up all my costs for this little adventure, I had wasted about $600. By going to the local shop for the repair, I had undermined whatever position I had to take the first AU-717 back to the seller.
So I must confess that I am a fool sometimes. Those who cheated me have more to confess than that.