Yes, every time, but only because the decision has already been made to buy a different type of gun.
As happened after making the decision in early '09 to buy my first Enfield, the last of the cheap ammo was gone within about two months (SAMCO was the last distributor). As a precaution I ordered a case from them, and then more from a friend's buddy.
Even if your next caliber is Not becoming extinct in terms of cheap surplus, the price could easily jump due to an unpredictable mix of factors or speculation. It could be global economics or a single new Supreme Court justice.
By the way, isn't all of the low-cost 5.45x39 (AK-74) ammo produced in Russia? Most liberals don't like military guns with larger mags, or their ammo. Isn't that having most of the AK-74's "ammo eggs" in one basket?
With Lebanon, Syria and maybe Iraq sliding into civil war, with factions in all of these countries incited and supported by the Iran/Hezbollah axis, imagine future transportation costs if fuel is driven by speculators to $4.50-$5.00/gallon this summer (even without Israeli Air Force deep interdiction missions).
A few years ago, about a dozen guys on Wall Street and the Chicago Board of Trade had a majority influence on our fuel prices, and issues were not nearly as sensitive as they are now.
If I could justify the cash to 'somebody', I would buy $3,000 of ammo right now, partly for my next caliber.