Older EM shuffle bowlers can be had pretty cheap, especially the ones from the mid-to-late 70s. Most people want the solid state ones for better reliability, more game modes and sounds. Lloyd @ Coinopwarehouse in Maryland probably has dozens of solid state shuffle bowlers at any given time and usually priced reasonably since they're projects (not fully gone through).
EM shuffle bowlers can be had for as low as $200-300 or less, depending on working condition. If you're patient you will probably find someone about ready to give one away as they're a harder sell unless they're super nice cosmetically or are one of the more desirable EM models.
The solid state ones are usually somewhere in the $400-800 range as working or non-working projects. Earlier Williams solid state models would be on the lower end of the range. IMO there's not too big of a difference between the later Williams solid state shuffle alleys running on Sys11 boardsets and the earlier ones.. better sound/speech, but it's a shuffle alley and it doesn't add as much to the game as it would in later pinball games for instance.
Fully shopped and ready-to-play solid state alleys offered by amusement companies are more likely to be in the $1200-$3000. So if you aren't looking for a project and don't want to have to deal with any of the electronics, it'll add quite a bit onto the price tag.
As with anything, if you're patient you're likely to find one pop up in your area at a pretty cheap price as people moving often "just want it gone".
Here's an eBay listing for a $750 Strike Zone (earlier Williams, from 1984):
ebay.com link: WILLIAMS STRIKE ZONE PUCK SHUFFLE ALLEY BOWLING MACHINE 1984
Personally I have a Black Beauty Shuffle Alley, one of the few shuffle alleys that Stern Electronics made and they used the MPU-200 boardset in it -- mustn't have been many of them made because you rarely see them pop up anywhere. With the BLUE led displays in it that I sell, it looks pretty sweet. The limitations of the earlier sound board used (SB-100 for some reason, despite the SB-300 being used in most MPU-200 games) really don't bother me at all in a pinball machine. Tones and early electronic melodies, no speech.. but it works for the shuffle alley just fine. So while I don't care for that sound board in a pinball machine, it's "good enough" for a shuffle alley that's exciting on its own to play with a group of people because you're all egging each other on, talking or joking while waiting for your turn again (which comes around pretty quick) and the sounds don't matter so much. Just my opinion 
ballystern_retrofit_shuffle.jpg
In terms of fun-factor, shuffle alleys are awesome when you're entertaining groups of people. No one has to wait long for their turn and it's some fun competition. The later alleys with the different modes like FLASH keep it interesting too.
