There is no single number because “waterproofing” covers repairs that differ by a factor of fifty. What you should be asking is which repair your basement needs, because that decides the price far more than any contractor’s rate card.
By Repair
Outside corrections — extending downspouts, regrading, adding a window well drain — commonly run from a couple of hundred dollars up to about $2,000. On a meaningful share of Michigan houses this is the entire fix.
A sump pump replaced is usually $400–$1,200 installed. Injecting a single leaking crack is commonly $400–$900.
An interior perimeter drain with a sump, which is the standard answer to water appearing along the wall-floor joint every spring, commonly runs $8,000–$15,000 on a typical house.
Carbon fiber straps for a wall that is bowing are commonly $600–$1,000 per strap at four-to-six-foot spacing, so one wall usually lands between $3,500 and $8,000.
Full exterior excavation and membrane is $15,000–$30,000 and up.
Why Quotes Vary So Much
Because they are frequently quoting different repairs without saying so. One contractor looks at your downspouts and prices regrading. The next prices a full interior system for the same puddle. Both may be competent; only one has diagnosed.
The other big variable nobody mentions upfront is reinstatement. If your basement is finished, interior drainage means demolishing and rebuilding walls and flooring around the work, and that can cost as much again as the drainage itself.
The Question That Sorts Contractors
Ask what route the water is taking to get in, and how they determined that. Someone who has walked your perimeter, looked at where the downspouts discharge, checked the grading and read the stain lines will answer specifically. Someone who has not will talk in generalities about hydrostatic pressure and move to the close.
Full ranges with the reasoning behind each are on the costs page, and inspections are free.