Those $200 solenoids may be a massive overkill.
I just ordered a couple of $15 samples from "valves4projects", a small Arizona outfit that is geared to DIY solenoid applications. My usage will be for low-pressure water, but several of the solenoids they listed can handle air and vacuum purposes too. All the business is eBay storefront at this stage.
Even so, solenoids may require more current than an Arduino output can drive, so I've been advised to use a Darlington Array (two npn transistors) technique to support 12VDC 0.6A current.