I did say "Usually". Always exceptions. Heading to a large match is NOT the time to do a "drop in" purchase.
I've always found a call ahead and a credit card work just fine. And just let your fingers do the walking. If you don't like the price quoted, try another. Or better yet, use the 'contacts' page from the club you are heading to to get a recommendation. An IDPA match in Florida had me driving to a warehouse park that didn't look all that inviting, but once I found the right door, it was a small shop run by an Army Vet who managed the warehouses, but guns were his passion. Probably the best price I've ever paid for brass cased .45 came from that shop.
And yea, coming into MA is unique, but us going other places is usually an eye opener for people used to the way Ammo is sold in MA.
Heck, in some states where the population isn't dense enough to support specialty gun shops, you'd be amazed where you can get ammo. In Idaho, I was directed to a local BOOKSTORE! Sure enough, the owners were shooters and they carried all kinds of stock. In fact, I'd say about 40% or more of their store was firearms/hunting related, but the only outward sign was "Hunting licenses sold here" on the door. Wouldn't be surprised if the book sales were the lower of the two incomes.
In Wyoming, one small town I stopped into just had your stereotypical General Store and the ammo and beer were in the same isle.
I'm sure today the pickings are not as plentiful, but I don't see why you can't call ahead and at least see before dealing with shipping ammo.
Many carriers allow you to check a limited quantity. Worth looking into for an 'emergency' stash or such. Also good for bringing home the 'leftovers'.