To do conventional hacking, it isn't necessary to have particularly expensive equipment, just computers (desktops or laptops) that are powerful enough to do their job without unnecessary delays, and maybe some off-the-shelf equipment that is designed for the use of penetration testers. The most dangerous tools in a true hacker's arsenal is software development software and the knowledge of what to do with it.
The main weapon in the arsenal of hackers - professional or otherwise - is knowledge. By knowing the exploits, these people are able to use them. Likewise, such hackers are able to protect themselves from others who would use those exploits against them, unless they are foolishly overconfident, and don't believe that others would be trying to hack them.
However, it is not impossible to hack the hackers. A search for 'scam callers hacked' would reveal a few videos by groups claiming to have located (and even taken over the security cameras within) call centres where 'script kiddie' call centre employees cold-call potential victims, phishing for those foolish enough to let them into their systems, and then use pre-made tools to exploit the openings.
However, a group with 'dangerous hackers' is likely not a bunch of script kiddies. If they suspect that anyone would be interested in stopping them, whether the police or counter-hackers, they are going to take precautions much better than the average person or business, maybe better than most governments. The developers writing the penetration software are probably going to do most of their work with their machines air-gapped, so that the only way to reach them is by taking advantage of the rare times when data is transferred from the outside via physical media.
I would hesitate to put a value on the knowledge and software available to such a group of hackers. Firstly, they wouldn't really need to buy software when they can simply steal - or write - it. Secondly, hacking is a specialised branch of Information Technology, and true experts are rare and can command large salaries, or hack their way to large amounts of ill-gotten gains in order to fund themselves.
So much for conventional hacking... but that's not the limit of what can be done. If a group can afford a quantum computer of sufficient capacity, they can be used in conjunction with Shor's Algorithm to crack many modern encryption schemes. This means that with a powerful enough quantum computer, a hacking group could crack many encrypted systems in a non-prohibitive time. Unless the targets changed their keys on a schedule that would prohibit quantum derivation of the keys from being useful, there would be windows of access to their systems that they might not anticipate... unless they anticipated this, and took advantage of post-quantum cryptography.
A quantum computer capable of cracking modern secure communications is currently theoretical, but is predicted to be achieved 'soon™'. There are commercial quantum computers for sale, though as the technology develops, the prices are changing rapidly... but this is where you could sink your millions or billions of dollars.
There's a saying, you can have a thing fast, cheap or good, pick no more than two. With a hundred trillion dollars, you could afford to throw an army of experts in quantum computing at the task of building a quantum computer soon enough to be able to hack your opposing hackers.
Once you have the other side's cryptographic keys, the task of hacking the hackers becomes a relatively easy job for the conventional hackers.