Brazil is buying 250 Leopard 1A5 tanks from Germany, for $500,000 each. The 1960s era, 43 ton, Leopard 1 has a 105mm gun, and a top speed of 65 kilometers an hour. It's the match for anything any of Brazil's neighbors have (unless Venezuela buys Russian T-90s). Brazil had previously bought 128 Leopard 1A1s from Belgium in the 1990s, and has already received some of the Leopard 1A5s (all of which will receive some additional enhancements in Brazil).
Until the 1980s, the Leopard I was considered one of the best tanks available. Entering service in the late 1960s, it was the first post-World War II German tank design. Although a contemporary of the American M-60A3, the German tank was considered superior. For this reason, Germany was able to export Leopards to many nations, including Australia. Most of the 4,744 produced (plus 1,741 Leopard chassis adapted to other uses, like recovery and anti-aircraft) have been retired (in storage) or scrapped. Many owners may have to melt down it's Leopard Is, for there's not much of a market left for 44 ton tanks, even those equipped with a lot of nifty upgrades. The original buyers of Leopard I have already flooded the market.
The export market is further clouded by legal restrictions, as Germany still retains the right to reject any buyer for the tanks. Thus prospective buyers must pass muster with German public opinion. No nations suffering from bad PR need apply.
The second hand Leopard I market is made worse by the availability of the Leopard II. This is basically a contemporary of the U.S. M-1, and often considered superior to the M-1. But the M-1 has an impressive combat record, and few Leopard IIs have seen any action at all. Still, on paper, and in training exercises, the Leopard II has been impressive. Some 3,000 Leopard IIs are out there, and Germany is still marketing them. Many surplus M-1s are available, and a few Leopard IIs. Add to this the thousands of late model Russian tanks available, and it's no wonder why second hand tanks like the Leopard I go for such low prices.