Your startup should never have to pay $$$ to pitch to potential investors. Period. Jason Calacanis authored an epic post on the topic of paying to pitch as well. It’s a great read.
Just remember that no matter how hard it is to source funds, your startup should never have to cough up its own funds. Nominal fees that cover cost of attendance are somewhat ok, but if the fees seem like they could pay overhead for the whole year for a potential angel investor group, then I would pass.