I don't get it. A 1991 is almost 20 years old. That should be pretty mature.
I don't know where you're from Manton, but in the US, and in CA in particular, wineries do not undercut their retailers by selling for less at the winery. In the US the winery sells to a distributor who sells to a retailer who sells to you.
Since you like your wine mature, you may know a bit about wine and how the business works - most distributors would be pretty PO'd if they knew the wineries were undercutting their customers - i.e. the retailers - by selling directly to customers at lower prices. That's one of the reasons there's so much contention regarding direct shipping today.
Prices for Ridge can vary considerably, depending on who's selling. "Regular" retail for something like Lytton Springs is around the low thirties these days. I've seen it for up to $40 and if you look for the 2007 for ex, it's anywhere from $20 - $40. The winery is never going to compete with the discounters so I wouldn't expect Ridge to sell it to me for the lowest price available.
And if they're selling back vintages, as posted above, it's well worth paying a few bucks more for perfect provenance. BTW - Ridge does offer a substantial discount if you buy from their mailing list when they release the wines. After that, the wines go for regular retail. They've been doing that for around 20 years or so - which means you made a mistake in not picking up that 1991 back then.