I was just curious about insurance for owners of more than one bike. Awhile back, I had a second car and the insurance cost almost as much for it as it did for the first one. How does that work when buying a second motorcycle?

You will pay the MCCA fee again, every vehicle in this state must pay it as part of their insurance policy, 2 bikes, you pay it twice.  You may see a break for multi vehicles but it's hardly noticeable, it pretty much can double and depending on type of bike perhaps a whole lot more.  Remember, unless you've got first party medical you should add it to your motorcycle policy, in Michigan motorcyclists get screwed over, all motorcyclists pay the MCCA fees but can only collect in certain circumstances, for example bin the bike in a low side in a curve and your medical is all on you, even though you've paid the fees.  ABATE was more interested in getting the helmet laws changed than fixing Michigan's screwed up insurance for motorcycles..  

At one time last year I had 4 motorcycles and 2 autos registered and I was absolutely bleeding cash, the insurance was killing me owning 2 sport bikes and 2 HD's, I've sold off both sport bikes and keep only my '13 Wide Glide registered, my old ShovelHead is currently being restored and will never again see the roads in Michigan, I'm outta here and back in Florida.  Last week I just traded both my '14 autos in for one '14 SUV, my auto insurance dropped by exactly half... Michigan certainly inspires a less is more attitude  


Edited to add:  I should have told you, I did quite a bit of checking and my motorcycle policy is through Markel, they specialize in motorcycles and power sports only and had the best rates and a good reputation when it came to claims.  Companies like Progressive use credit reports to base their rates but also use their own creditworthiness formulas to determine rates along with the type/value of the bike, Markel is strictly CR and bike, if you've got good credit you will get a better rate.  Markel was over $600 lower than Progressive for my 4 bikes, now with one bike registered with full coverage at the maximum levels of coverage my WG is $366 a year, of course now add in the MCCA fee of $186 and it's $552/year, much better than the almost 3k a year I was spending, that $744/year in MCCA fees hurts and those sport bikes were just not worth the price of admission  

http://www.markelinsuresfun.com/products/motorcycle