Mike, you are correct, there is a correlation of a homes actual sale price to the assessed value of a home. I'm not sure about Grand Rapids, but in southeastern Michigan the values were usually between 1.8 to 2.25 times the SEV. This has decreased quite a bit with the glut of foreclosures and "short sales' in my area. The new values are quite startling.
A local real estate agent would be able to pull information from public records to give you the range for East Hills. Keep in mind, this is a general range. There are always homes with desireable floorplans, locations, and condition that will have a higher ratio. If your area is in a declining market, the Taxable Value will reach the SEV within a few years, depending upon when you purchased.