Hello C.,
A crankshaft (the part alone) is typically not that expensive, but the intense labor to replace it is.
If you are mechanically inclined, have the tools and have the service/repair data it's not that bad of an ordeal. If you are missing one or all the needed prerequisites, you will pay a hefty sum to have the work performed.
Worse yet, is finding anyone qualified.
Most modern small engine techs I come across at dealerships around here are washed up types that could not find a job doing much of anything else. Most of the good ones have moved on to different careers or struggling to go independent.
Like I mentioned earlier, we need some pictures of what you are dealing with, otherwise this is all playing imagination games without any visual content/context.