how is there a cross tolerance? like i know they are both GABA agonists
How is there a cross tolerance? + like I know they are both GABA agonists = oxymoron lol
You just answered your own question. Both of them enhance GABA activity in the brain, providing the "soothing" and "sedative" effect. Anything that stimulates GABA in your brain you will have a cross tolerance to. You will and should however, only have a tolerance to the mechanism of action of the drug, meaning that you won't be able to just equate "one xanax to three beers" etc. Doesn't really work that way.
Xanax is very lipophilic, and enters your system rapidly reaching your brain and begins working in 15-20 minutes in most cases, and it is engineered to act that way. Alcohol however varies greatly on a person's body shape, size, metabolism etc, making it's ability to affect the brain a bit different than Xanax. They are both GABAergics, they both effect the brain's GABA activity in a similar manner, however Xanax's mechanism of action and ability to better bind to those receptors is what makes it more addictive. You may find that it is "easier" to drink more alcohol than normal if you have frequently been taking Xanax, but once again it's mechanism of action is not going to be as quickly or as strong as Xanax, so it will sort of "feel" similar and you will have more of a tolerance over a non-drinker/non-benzo user.
Xanax is, in my opinion, is a much "cleaner" and more efficient way to enhance GABA activity, acting within just a few minutes and includes none of the negative side effects that alcohol does. They are both drugs that let more GABA enter the postsynaptic neurons, however, Xanax does it more quickly and more efficiently.
In short, I highly doubt that if you are taking 5mg+ Xanax a day recreationally, then consume alcohol heavily one night it will have little if any impact on your Xanax tolerance. Now, if you were a heavy drinker and heavy benzo user, that's an entirely different story.
Careful taking too much of either one for a prolonged period of time. Benzo withdrawals are a bitch