I think thats more because sabots (and maybe talons) are a bit too strong and less because buffalos are any good.
Yeah, but what platform can pack as much per DP? It's 1 med missile + 3 small missile + 2 Tac lasers + Talon wing (slow replenish) per 4 DP, and 2 Vulcans to not get swatted by missiles right away. No armor or shields, but you can do without them if you suppress enemy with sabots.
Sabots are strong, but also very limited. For normal ships going Sabot heavy means crippling long term play. But Buffalos have no long term play to speak of, so for them it's not an important drawback.
Anyway, player can't use such attrition tactics in campaign. Plus they are definitely not fuel-cheap, only supply-cheap. But in a narrow sense, Buffalos are worth their DP cost alright, if correctly built.
Pirates running around with Buffalo stampedes could be fun though
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