Matchday Pricing

[DJ]

Hi all, can anyone clarify the pricing structure for the matchday return special fares?

I paid £3 a couple of weeks back to get to the Hawthorns and back from Wednesbury Parkway, however, the ticket was valid from Bilston Central, as the conductor hadn't updated his machine. However, on Wednesday I was charged £4.50 for the same ticket, but valid from Wednesbury Great Western St (so not even where I got on!). It's all a bit confusing and I can't find any clear information about it at all on the Metro website.