If you are a one customer business, don’t count on sticking around for so long.
With 100 customers, you can experiment with things like raising prices, changing advertising models, lowering costs etc.
You can’t test anything with one customer because a single mistake will destroy your business. Moreover, having just one customer is boring and you will be a slave to that customer.
Whether it is easier? In my experience, it is far easier to sell 10k to one person than to gather 100 people but it is not always sustainable.