Many loudspeaker cab manufacurers use the least expensive speakers that they can get away with whilst charging phenominaly high prices for the finished product.
Some few short years ago two of the most popular cabs from a leading UK manufacturer retailed at £499 each, these being a 4x10 and a 1x15, the 10" & 15" speakers left the actual speaker manufacturer for approx £9.50 (10") & £32 (15") each which equated £461 £467 for the empty cabinets which were basic tuned cabinets, nothing complex.