From country to country, the legal status of bitcoin differs significantly, and, in most countries, it is still undefined or changing. The main reason for this is the novelty and the cryptocurrency phenomena, which is why many governments are still exploring the possibilities of this digital asset. Whereas the majority of countries do not make the usage of bitcoin itself illegal, its status as a currency (or a commodity) varies and implies different regulatory consequences. While some countries have explicitly allowed its trade and use, others have banned or restricted it. Likewise, various government agencies, departments, and courts have classified bitcoins differently. All of this refers only to bitcoin, but, a similar system is used with other cryptocurrencies.
In other words, very few countries have gone as far as to declare bitcoin illegal but that does not, however, mean that bitcoin is “legal tender“. However, just because something isn’t legal tender, does not mean that it cannot be used for payment – it just means that there are no protections for either the consumer or the merchant, and that its use as payment is completely discretionary. Currently, only Japan has gone as far as to give bitcoin that designation, and in 2016 Japanese financial regulators proposed handling virtual currencies as methods of payment just like conventional currencies. It should be noted that India is also in the process of creating a legal framework for bitcoin use.
Considering all of this, the question should be reformulated. What does it take, rather than how much does it cost, for a country to legalize Bitcoin? It takes changing the law rather than investing money for Bitcoin to become legal. Of course, in the process of legalization, there are all sorts of expenses, but that differs from country to country.