A Rollem Insignia 5 will get the job done. It is a significant, but necessary investment ($140k) for a production sticker plant, and will allow for high volumes and competitive pricing.
For the casual recreational printer you can hand cut the backs with an Olfa top sheet cutter (<$20). Of course, the labor cost to slit each sticker by hand would far exceed the wholesale cost of the sticker purchased from a professional printer. I don't recommend it, but you can also use a high-quality plotter to kiss-cut the back of printed material (which usually results in many square yards of ruined material as the blade quickly dulls cutting
paper fiber, in addition to alignment issues).
I've mentioned before that being competitive in the sticker business requires an investment in the $500k to $1M range. Without the proper plant and sophisticated sales, fabrication, materials handling, and shipping operations (and the sales volume to support it), there is essentially no way to be even close to profitable in this segment (unless you are over-charging your customers). The average
sign shop or large format printer will be doing themselves and their customers a significant service by out-sourcing sticker production.