We play with the Research & Development (aka ‘Weapons Development’) optional rule quite a bit now, most recently in Axis & Allies Global 1940. The way we play (correct?) is that if the research has failed (i.e. not rolling a ‘6’) then the research token is still alive and available to roll for again in your next turn. You don’t lose the token on failed research, and thus don’t have to buy another one to roll again next around.
Does that make any sense?