Since you need two of everything, or more, two switches, two physical links, (hopefully) two physical racks or cabinets, and all that, it's minimum x2, but nowhere near x100. The cost for additional physical transit links is generally pretty reasonable, depending on provider, if you have more you can negotiate better rates, same with committed bandwidth. You can get better rates if you buy more.

There are a lot of aspects to that, but the cost of doing all of the above is a lot less than not having it and failing to have it at the wrong moment and losing money that way. Each business needs to weigh their risk against how much they want to invest and how much they think they can tolerate in terms of downtime.

Seems logical thanks for engaging with the question.