The thing about drugs is that, when used long-term, they stop working. They will most likely end up making you more depressed and they will leave you constantly craving more. It doesn't matter how much money you have, it's not about that. It will usually become a compulsion. You will find yourself needing more and more, and the effects will become less and less over time. It depends which drug you choose to use, but they will all eventually lose their desired effect.
Even if you have an unlimited budget and source, drugs will begin to damage your psyche, which will in turn prevent you from being able to feel the pleasure you're looking for.
There will be issues that could arise such as:
Physial dependence (which will be harder to control as your tolerance grows) You will need more and more with increasing frequency. There is no cap to this effect. There is not ever going to be a time when you think "okay, this is enough"
Social unacceptability (which will make you lonely when all your friends are unwilling to associate with you and society at large rejects you) It will likely make people think less of you or be suspicious of your intentions even if you don't intend to scam or rob them, it's just part of the stereotype and it's very difficult to conceal long term drug use. Even if people don't know all the details, they'll be able to tell something is wrong.
Health concerns (because drugs are very hard on your body) Things like heart problems, severe liver damage, extreme weight loss, frequent vomiting, sexual dysfunction, various infections, respiratory issues, dental problems, eating disorders, hepatitis, HIV, and a whole slew of other stuff depending what drug you choose to indulge in.
Negative changes in your appearance (which will be a blow to your self-esteem) There will be changes to your weight, skin will lose any radiance and probably break out more, teeth are likely to go downhill, hair gets brittle, the drugs will come through your pores which will make you smell bad, you'll age very quickly.
Mental obsession (which will make it difficult to think about anything other than drugs and leave you constantly chasing a feeling that you won't ever find again) The only thoughts you have will become centered around drugs, even when you are high. You will just be constantly longing for more.
These things might not all apply to you but enough of them will for it to be nearly impossible to be "happy" no matter how much drugs or money you have.
It might feel euphoric at first but then you'll rely on that high as the only pleasure you're able to feel anymore and when shit comes crashing down and you aren't able to experience that high that is your only source of pleasure, you won't be able to experience any sort of pleasure. Sex, food, love, friendship, family, and achievements will be nothing. They will bring you no pleasure.
And that's where the real misery will begin. It won't matter how much money you have.
That's what they mean when they say "One is too many and a thousand is never enough" They mean that there is no amount of drugs that would leave a drug addict feeling satasfied.
Source: I'm a (clean) drug addict.