I noticed in pictures of the innards of several top machines (Speedster and Cyncra) that they were using Parker-Hanifin solenoids. I've used those in industrial settings, in HVAC and as an electrician. I emailed Kees van der Westen:

Hello; I have seen a picture or two of the insides of a Speedster and it looks like the solenoids are Parker-Hanifin, is this correct? Are these of a more robust design then the average espresso machine valves? I've used them and Asco brand valves in my years in industry. This subject has come up on HB in terms of LM GS3 reliability and espresso machine reliability in general.
Thanks, KDM
PS: May I post your answer on HB?

His answer (with permission) :

Hello KDM,

We have been using these Parker valves (2-way/2.5mm orifice, 3-way/1.5mm and 2-way/6mm, all with Viton gaskets, no Ruby) in our Mirage series for 10 years without ever noticing they go wrong quickly. Don't know if these are available in different levels of quality.
Sure you may,
All the best,
kees

Could this be an answer to some problems with solenoid valves in other machines? Could Parker solenoids be retrofitted where room exists and failures have been recurring?
KDM

Do you know the model number of these valves? I am looking for small valves for some mods I am considering for my espresso machine.

I don't have any particulars but search up Parker-Hanifin and ASCO, these two companies make all manor of solenoids.

http://www.parker.com/portal/site/PARKER/menuitem.7100150cebe5bbc2d6806710237ad1ca/?vgnextoid=f5c9b5bbec622110VgnVCM10000032a71dacRCRD&vgnextfmt=default&vgnextcatid=5777193&vgnextcat=INDUSTRIAL%20SOLENOID%20VALVES&Wtky=VALVES

http://www.ascovalve.com/

You won't find a bargains from these two but it may be worth it in terms of longevity.

Any idea on cost? Like are we talking a few bucks for a few hundred bucks for a small solenoid?

*EDIT: Never mind I found my answer http://www.valvestore.com/products.asp?dept=1467 and http://www.thevalveshop.com/menu/auto/asco/8256.html

So at least in the small sample you linked to price seems reasonable. If these gave longer service then the OEM valves higher prices would be justified, IMHO.
KDM