There is no simple answer to this.
For BD the cost will be on the high side as BD has no
infrastructure in place. Others like Pakistan on the low side as they already operate many dozens of F-16s.
My guess is that BD will be looking to pay around 4 billion US dollars for 24 latest block F-16s, this will include the cost of converting the airbases to handle F-16, maintenance for first 5-10 years, training of pilots, bombs and missiles and the actual planes themselves.
Although this sounds a lot, remember that Western aircraft are more reliable and have higher life expectancy in areas like engines than either Russia or Chinese planes. BD pays more now but gets the payback over the life of the plane.