I don't know exactly how much money they have to build a casino, but I suspect it's a significant amount of money just to get started, not to mention the money they'll spend on promotion.
But then again, it's a small amount for them once they're successful with this business. It does take time to build a large, well-known gambling platform. It's also not uncommon for them to fail to pay out winnings. I don't know if this is because they're bankrupt or if they were intentionally deceptive from the start.
Only Wolfbet know about this figure but I am quite sure that running a business in many years is not simple and in financial aspect, it requires a lot of operation cost including development, security, maintenance and marketing.
To survive in a very highly competitive gambling industry, Wolfbet must have a very good business model for their operation and they surely are a profitable business. Without profit, a company can not exist for years like Wolfbet and they have been already surviving in about 3 market cycles that is impressive.
Now, this is also something to note: on this forum alone, there are many well-known casinos, and competition is indeed fierce. However, if they have earned a high level of trust, they will be able to compete. Users can certainly see that.
Yes, they won't last long if they don't have sufficient capital and profits. Eventually, some casinos fail to pay or openly announce their closure. As a note, user comfort must be a top priority, especially in terms of prompt response to user complaints.