OP's question and many of the answers simply show that the difference between any two fare buckets requires you to read the fare rules. There is no substitute for it.

There may be some general conditions, e.g. that BE tickets are non-refundable and do not generate a credit if cancelled and cannot be changed. But, when it comes to comparing to a discounted standard non-refundable ticket or a refundable or flexible ticket, there are no general rules.

There are tickets which may be changed without fee or with a fee. Tickets which may be refunded but with a fee or without.

Fare rules change all the time, so the fact that someone you know had one experience means nothing. More importantly, the fact that someone you know caught a break from an agent does not mean that you will.

So, given the amounts of money involved, it pays to spend 2-3 minutes reading these things.