I have the $30 Slime pump and have used it many times to seat the bead on my 950's rear tire-and to make it worse, I like the Heidenau tires, which have one of the stiffest casings I've ever worked with. The Slime pump will get me the 90 or so PSI I need to seat that PiTA tire.
Just remember not to let it run for more than 5-8 minutes at a time, then a commensurate rating period in between. Apparently the cheaper one has a plastic piston, and is even more susceptible to the heat caused by the pump doing its job. After all, one of those laws of physics has the temperature rising with pressure...
I consider it to be "essential" to my tool set. If it broke tomorrow, a new one would immediately take its place. I do carry a small bicycle pump as back up, but never had to use it.
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