THERE IS NO SUCH THING AS BASIC TRAVEL ALLOWANCE!!
Please remember: there is NO such thing. There is NO such requirement, in any country of the world. This is an invention of the scammers.
(another term: STF - standard transit fee)
There was such term in 3rd world countries and ex-commy countries, but it meant a totally different thing. For example in Russia, when it used to be a communist country, it was illegal to possess or exchange foreign currency. You could go to jail if they found dollars on you. The only exception was for people traveling abroad, they were allowed to exchange certain amount of currency (thus, the term: allowance). Note: allowed, not required!!! It was never a requirement, but more like a privilege. There was no minimum set, but there was a maximum, very limited, in ex-USSR for example it was allowed to exchange 500 rubles.
Same in Africa. Those times are gone, and this term doesn't exist anymore. But scammers "revived" it and put a new meaning into it, to scam victims out of more money, like as if it's a "requirement".
Another variation of it, widely used by Russian scammers: the Embassy requires to show money at the interview, to prove she has money for a trip and to support herself abroad. There is NO such requirement. It is also clearly stated on the US Embassy website, btw.
The applicants for visa may be required to prove they have sufficient funds to support themselves, but not in the form of cash shown in the window during the interview, comon!! The applicants should have good jobs, bank accounts or present a letter from the inviting side (affidavit of support). This is how they should prove, and not by showing a bunch of cash weeks or months before departure date, which can be simply borrowed from a neighbor for couple hours, just for the interview. They are not that stupid in the Embassy.
Bottom line: Basic travel allowance (BTA) to be shown in the airports, customs or Embassies is a baloney!!! If somebody mentions it, it's a 100% scam.