That is right on target.
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Personally, I do like if not love commissions, as part of my pursuit to obtain custom artwork made for me personally, as well as the connection with the artist. I'm less interested in buying someone else's commission regardless of rendering quality, at that point I'd pass and either commission my own or buy something published, but that's just my personal preference.
Right there with you. While it's really nice to work with the artist to get it right, I fully expect that my estate will lose 50% or more on what I get.
After all, how many people are going to want a Sugar & Spike cover by Hembeck or Katie Cook or a JLA 29 riff featuring Scott Shaw!'s Captain Carrot, the Zoo Crew, and the Justa Lotta Animals? I like them, but I doubt that they will sell for much.
Even my published pieces tend to be "odd," e.g., FCBD cover by CPW3 for Stuff of Legends or three pages from Huck - a good book that I doubt will be a big seller.
Buy what you like and can afford! That's my best advice.