Collectible and classic amps are not always the best sounding amps. For example, there's a lot of not-great sounding Marshalls from the 70s and 80s where they used whatever component values they had on hand that day and the end result is kind of "meh." However, they're still valuable to collectors or enthusiasts on the market.
Another example is with vintage guitars. Hard truth to swallow: most vintage guitars don't sound or play that great. Sure, they have "mojo" (whatever that is) but they're often temperamental, hard to get the pickups balanced, and more difficult to get to stay in tune. Modern reissues/reproductions are almost always better sounding, better playing, more stable instruments. However, the vintage instruments still command very high prices because of collectors.
Best sounding =/= Most Expensive.