Can anyone tell me please, is there any good but cheap websites to buy Xanax (alprazolam) without a prescription?

NO! Xanax (alprazolam) is a controlled substance and only available by prescription; any website selling this without a prescription would be in violation of federal law and subject to prosecution.
If you buy online. If you buy this online -- outside a regular pharmacy and without a physician's prescription -- you have no guarantee of receiving the correct product. They could send you anything and call it "xanax (alprazolam)." as my colleague indicates, xanax (alprazolam) is a controlled drug, and is legally available only by prescription.