Loved it last year, but being in the Thames for 6am took some dedication. Wasn't impressed with the quality of roads or lack of drafting marshalling going on, but all other staff were excellent. I'm lucky enough to live close enough, not to also have to pay out to stay somewhere as well, but still find it an expensive day out. Like Schmu will be looking at other events like Bath as a cheaper option.
But like London and Blenheim, if you haven't done it before, you should do it at least the once just for the experience.
I dont know how you can compare a sprint tri at Dorny, which happen every week almost to an iconic end of season race. I think you mist have spent too long in Weymouth
It depends on your standard. Yes there's something going on every weekend at Dorney, and also mid week at the height of summer. But for a newcomer they are very well organised events. With well thought out pre-race notes, and a lot of helpful friendly staff at all stages of the race (Same as Windsor and London).
While someone who runs over Boxhill without breaking into a sweat, can't see the point of it, something like Dorney is ideal for a first OW event for newbies. Windsor and London are the same, good initial stepping stones. The cost is relative to what you will get out of it, as someone who only started OW Tri events this year they have been well worth the cost.
For others Germany and Switzerland IM holidays are the only thing worth doing, and for others still Norseman is the only challange worth splashing out on each year. Courses for horses as they say, you pay your money, you make your choice.
(Anyway gets you out of Weymouth for the weekend )