You got v lucky boomy. I have only one DM within 10km of a VC and I got all their MM. I wasn't game to ask them to order in from other stores as I felt I had done so well I feared some kind of karmic revenge would befall me!With respect to that manager I don’t think any DM stores did clearance on MM recently, regardless of their location. In fact I was in the Gold Coast last weekend and while my +1 was shopping in Harbour Town I was cleaning the local stores of MM. Some only allowed one bottle but none said no to the price match.
Another anecdote regarding socioeconomics, my local BNE DM which is located in a pretty good area had some dusty MMs on it's top Langton’s shelf. The manager said MM is not popular because most customers who choose to spend > $100 on Aussie Cab Sav usually go for SA or WA wines.
I'm not sure I'll get many more chances to get a Langtons exceptional classified wine on my budget so I'm happy with what I got even if I didn't get a vertical like yours.