There is virtually ZERO market for "collector" bowling balls. The term "collector" bowling balls makes me chuckle. I can't think of a worse "investment". I see guys on eBay trying to pawn off their undrilled "gems" for $300 and up ....... GOOD LUCK !!
I don't really see a collection of bowling balls as an investment. Although, some people probably do. I started buying balls as a way to learn about the differences, so I would buy them cheap with the plan to drill and see what the differences were. Then I bought a few that were "extras" of balls I really liked.
Some I bought because I knew I would be able to turn them around and make a few dollars. This was the case with the Storm Invasion and Anarchy. I bought 11 Invasions when it was discontinued for $75 each. Within a year I sold them all for $200+. The same with the Anarchy, but I only had 6 of those. But it's rare to come across that kind of opportunity.
I have picked up several clear balls over the years, just because I liked how they looked. Kinda like your grandama with those collector plates, spoons, thimbles or whatever else people collect.
For some reason, I grabbed every one of the Vibes prior to the new generation. I have the Bowlers Mart ones, overseas and special edition Vibes. The only one I'm aware of that I don't have is the Peach, which I still kick myself for not buying when it was available at the USBC Open Championships in Reno several years ago, but I didn't want to spend $200 for a freaking Vibe.
I have quite a few, but don't really consider it an investment. Kinda like my "collection" of Whiskey(mostly Bourbon and Rye). I intend to get good use out of them or liver damage, which ever comes first.