Was at Mondial de la Bière in Montréal last year, which was kind of run along those lines.
The 125ml was ok. Just ok. They'd a huge amount of stronger Belgian-style beers on offer, so get why they were using the 125ml glasses.
Personally though, I found it pretty annoying having such a small glass. A 4.5% red ale is gone in two or three gulps. IMO, that's not really enough liquid to taste and enjoy the beer properly.
Would point out though, queues were minimal and it wasn't an all-you-can-drink event. Coupons cost CA$1 (€0.70), with beers costing between two and six coupons each. €40 would probably be a decent enough price to go on here. Though people will make it their business to get their money's worth out of it.
Beer festivals, for me, aren't just about trying as many beers as possible, they're about sampling beers, getting a half pint of what you like and spending a good few minutes actually drinking that half pint.
Also, there's zero chance I'd be interested in any festival that involves frequent queueing.