@MartinLangmaid has written extensively on the topic of getting routable access to a carrier-NAT connected device (such as yours). For one such thread, see Pepwave Br1 Mini NAT Type [Video Tutorial Added] - #10 by MartinLangmaid
The $500 for a Verizon static IP address is a one-time fee across your account - for a consumer account that would be $500 for up to ten lines/ten IP addresses.
Good luck.
Z