Most alternative therapies are not reimbursed by insurance so you have to pay for them yourself. Generally the more expensive a therapy, the more evidence you should require that it actually works. But the extent to which cost affects your decision also depends on your financial circumstances. For some people $20,000 would be absolutely impossible to afford, for others it would be a trivial expense. If a therapy really is impossible to afford, then it doesn't matter how much evidence there is for it, while if you have no trouble affording it, then considering the stakes perhaps cost should not be much of a consideration.