One thing that is worth pointing out is a lot of geek conventions are pretty thoroughly commercialized these days and are little more than industry conventions and/or platforms for launching new products. When your primary audience is businesses (say, industry press) sending employees to an event, yes, the price of almost everything connected to that goes through the roof.
At least that's what I see out of, say, ComicCon. I don't give a shit about comics or anything related but the non-stop press coverage on some tech/gaming outlets (which I don't give a shit about either but I get contaminated through Google News) led me to believe that. I'm sure being a host organism for industry is probably pretty financially advantageous.
Furries will never see that level of commercialism. Even cons that have explicitly tried to create an environment like that have really not been successful. Because while the not-furry convention world has seen increasing commercial participation, the furries have most likely seen a precipitous decline in their average income and education levels over the last 15-20 years. There's a lot of reasons for that.
But anyway, cross-attendance. I think it helps to figure out what cliques within furry you're talking about. I think classic geek-types probably do have some level of cross-pollination but most of the new arrivals- the ravers, the fresh-out-of-the-closet transplants from East Bumblefuck, PA, whatever, probably have comparatively little interest in other geek fandoms. That's not why they're "here". I don't really know how much things line up over age/generation and time, but it's worthwhile to remember that there are sub-groups within furry that have fundamentally different archetypical personalities.