Has anyone sold over $35k worth of equipment over the net? How do you protect yourself?

Perhaps I am just paranoid. But no way I would ever do something like that. I would sell to a reseller or consign. Ever since I got ripped off as an 18 year old buying a used car, where the battery was charged to cover up it had no alternate, or fly wheel and could only operate for a few hours. The guys were at the bank cashing the check immediately. 

I also know guys that buy and sell $10K audio stuff. They seem really lucky to me. 

I've used lawyers as escrow agents. Not expensive, given the amounts at stake. Escrows are pretty common in all sorts of industries- an intermediary who receives the funds and holds them as a neutral, releases the funds once the other side advises that the goods have been satisfactorily delivered. That still doesn't account for the difficult buyer, but I've rarely had an issue. 

For big dollar purchases, you can do a "closing"- which can now be done virtually. 

The hidden defect, the things that don't show up in a pre-purchase inspection, are what will "get you" as a buyer.  As a seller, I try to be as scrupulous as possible. I've sold high end properties, collectible motorcars, vintage stuff that way. In fact, I'm doing a few deals now with vintage motorsports and will offer the buyer that kind of protection. But, I usually go the distance as a seller, and make sure everything is "right" before I put it up for sale. 

I’ve used escrow.com to good effect. The fees are relatively low, and transparently declared here. For larger amounts, it's convenient for the buyer to be able to wire the money to them, and they will then wire it on to the seller after the escrow is released.

The buyer assumes huge risk for something that expensive. I would do it in person only with the bank process described above about the car, if I was the buyer. At 35,000, traveling for pickup would be a pittance %wise. And I would want to check out the merch. I know you are asking as seller, but even as seller I would want it to be in person. At that price level there is too much risk for me otherwise, especially considering shipping. Otherwise, middleman like TMR is the way to go, bite the bullet for peace of mind.

I recently sold two items with TMR on consignment. I think they take 35% with consignment or you may choose to sell to them outright (for less money). They show the items on several different sites including their own site. It took a few months but well worth it (for me) to avoid the anxiety of selling to an individual. It was a pleasant experience.