For a little while after we got the new plane there were boxes arriving every week. A lot of minor things, like the collar for the circuit breaker, but some larger things, like the gust lock that the broker had to supply new from Diamond in Canada. That was a big box (for not that large an item) and had a lot of customs stickers on it.
The first plane had a cover from Bruce’s Aircraft Covers. It seems like they have changed a little in the decade between orders. The covers are made over in China, but I think the design is actually a little evolved and better. Sadly, they no longer offer monogramming of the cover. It seems a little silly, but I think it’s a bit of a hedge against someone taking the cover. (That’s a really small probability to offset. There are about two hundred of these planes in North America, the vast majority in hangars. Do I really think some other DA42 owner is going to sneak onto an airfield (some of the most secure property in the United States) and take a cover off my plane to put it on theirs?) Mostly I like that the pieces of the plane, including the cover, have the tail number on them.
The important thing to protect is the avionics suite. Apparently keeping the plane covered will keep the temperature in the plane lower. I want those avionics to last as long as possible and, unlike the previous owners, I can’t afford to keep it in a hangar. So for less than the cost of one month in a community hangar, we now have a huge sail of Sunbrella fabric to wrestle with in the wind at the beginning and end of each flight. I’m working on the clever methods for getting it on and off with the least trouble.
You can order covers for the entire plane. If I were in the Northeast without a hangar I might want to cover the wings, empennage, and engines cowlings. In places where there is ice and frost, it’s a great way to reduce your time preparing for flight. The plane is covered with the last week of ice and snow and you just undo the Velcro and, zip, you have clean wings.
Plugged
We don’t have ice or frost much here.
They also sell plugs for the engine inlets. Studying the engine cowlings for the first month I decided that the only real one to worry about was the large one at the bottom. On the first plane I made the mistake of thinking that since I had flown for over a year without seeing anything in the air intakes in the front of the cowling that it wasn’t something I needed to worry about. I learned my lesson. You never know when the little birds are the field are going to decide your airplane is the one that they want to nest in. So I bought the plugs for those two inlets. There was no option to monogram them, but a place in Los Angeles monogrammed onto a piece of matching fabric and then a shoe repair place stitched it on. (The monogramming place said the material that the plugs were made of wouldn’t survive the monogramming machine, which explains why Bruce’s Aircraft Covers stopped offering it.)
Flying Summers Brothers 
Bruce’s supplied the interior cockpit window screens for the Gulfstream IV-SP that I fly. I’ve always been a fan of their GA cabin covers, but for whatever reason, the G-IV screens seems rather flimsy and thin. They fabric stitched around the edges of the foil body started to unravel almost immediately. We had to send them back. It’s not like they were abused; we always stored them in the storage bag and they were kept upright in a closet near the cockpit. I suppose the “China” factor probably has something to do with it. But as you might expect, with the price they charge for that set (it’s for a Gulfstream so use your imagination), the low quality was a bit of a surprise.
In aviation I have learned that the price does not necessarily mean quality. Sadly. That was a difficult transition from the building trades, where it holds true pretty well.
What’s really sad is that your statement is true even up to and including the $40M+ intercontinental business jets. I could show you tiny plastic parts on my airplane that cost as much as my car.