Yeah, they can be a bit brutal on price with non-frequent customers. Luckily if you buy enough stuff from them at normal price, you can get their discounted pricing, which is REALLY deep. Like Like 40-50% off list price deep. At that point it's a no-brainer. While Heyboer/Hammond/Etc do make great iron, I truly do feel that if price is no obstacle, Mercury is the "best". Probably not the best bang/buck at normal prices though.
Sergio at Mercury knows his stuff man. While you have no argument from me that they aren't cheap, their use of grain-oriented laminations, Extrememly high temp vacuum impregnated potting epoxy, teflon insulated leads, and 150% over stock powerhandling, I'm hesitant to say it's all fairy dust.
I'm currently doing some testing with their SVT PT/OT/Fil set. A stock SVT is about 300watts or so, Sergio and Patrick assured me that this set can handle 450 without a sweat, which is exactly what I'll be doing. Using KT90's. Muahahahaha! I'm also using WIMA Polypropylene can caps for filter caps too. They're HUUUGE. Nearly the size of a soda can, EACH. ESR should be disgustingly good, and will never need to be re-capped.
I've also used their Soldano SLO100 set, and it truly slays.
The SVT set. Suckers are HUUUUGE. Laminations are a good 5" thick. Smaller middle tranny is for the heaters (this alone is the size of a typical 50W OT). Smaller toroid is the mids inductor.