I pay $100 per month but only because its a euro car. The IBC doesn't have data on the VIN so its insured based on value. This is regular insurance, not specialty. For reference my 240SX is ~$150 per month.
There are companies that will insure regular E30s as "classics". I dont have the names of those companies but the requirements are:
-Must be over 15 years old
-Must have a written appraisal done by licensed appraiser (including photos of interior and exterior)
-Must own another vehicle with liability (driving) coverage at all times, the Classic auto can’t be used to commute to work except on occasion
I've had both my 240SX and Miata quoted as "classics" and they came in at $108 per YEAR!