I work in the greater Chicagoland area so you may not want my opinion, but …
if you give me a justification that I can give to my manager to attend the meeting during business hours, I would attend. You don’t have to sell me, you need to tell me how to sell to my manger. It is just that simple.
I would think the low hanging fruit is either continuing education or an opportunity for my company to make a sale. Networking and socializing are things I cannot take to my manager.