Earlier quoted context omitted.
At least in the US, VOIP providers (think google voice or twilio) interconnect with telephone companies similar to how landline/cellphone companies interconnect with each other, so #1 and #4 are essentially the same. The only difference is what the "from" number appears as. If you look at the price lists of voip providers, you'll note that the only factor that determines the price is where you're calling to, not wher…
That provider is either only providing service to one country (very likely because this is separately regulated in every country), is showing you prices specific to your country, or is doing #1 and making themselves liable for spam.
twilio can hardly be described as "providing service to one country", and has the same price list whether I'm using an American VPN or Dutch VPN: