In not sure. Personally I like them due to practicality not price
Bugaboo cameleon - lasts forever, large carrycot, suitable for overnight sleeping, car seat compatible, forward and rear facing, can add snow wheels, great with buggy board, handle adjusts, large basket
Bugaboo bee - suitable from birth, folds in one piece, rear and forward facing, good basket, handle adjusts, small space on buses, lightweight for tubes/ escalators/ flying/ car
Bugaboo donkey - one of only few doubles that have rear facing seats, either carrycot or seats, suitable for overnight sleeping, takes x2 car seats, good with buggy board, converts to single if needed.