I agree with you get what you pay for when it comes to such things, although I've seen plenty of happy people with ebay specials I'm pretty sure I can get these ebay specials to heatsoak on the track in no time at all. I would also be worried with pressure drop and the efficiency of the core given their small size I would expect literally no lag but that's not the case from reading a few reviews on uk-mkiv and vwvortex, so it's a bit worrying. They also won't be efficient enough for those pushing deep into 300 bhp.
When I purchased my eurojet front mount intercooler - the street core so it wouldn't be too massive and laggy I was surprised when it arrived. It was absolutely massive at 2" thick 10" tall and 31" wide. Fitted it's pretty much level with my headlights/grills and reaches all the way down to the splitter. But have to say I was pleasantly surprised when I drove it, I didn't notice any lag.
Another point, given the small size of the ebay intercoolers I would have thought fitment wouldn't be a problem, I mean my eurojet core is absolutely massive compared to them ebay cores and I've managed to fit it behind a standard 1.6 bumper with minor trimming only on the middle grill not anywhere else. Seems the ebay cores are as awfully designed as people claim.
We all love a bit of whoring