I live in Dallas TX and Columbia SC. When I had my air conditioning and heating serviced by different companies in both cities, on each occasion the service man emerged holding a blower motor capacitor in his right hand, saying that the voltage was low on the capacitor and that the unit needed replacing.
I told each to go ahead. [This item costs $10.08 online plus shipping.] The Dallas company charged me $89 and the Columbia company charged me $136. The Dallas company (OneHour AC & Heating) was doing the service on an annual prepaid contract. The Columbia company (Gene Love Plumbing & Electrical) called me, since I am one of their plumbing customers, to set up an appointment for a "free" air conditioning/heating service call. Gene Love also added on a "Diagnostic Fee" of $137, but waived it because they are a "Service Partner" (whatever that means).
Service people can charge whatever customers are willing to pay. So, both of these companies are in their rights to charge whatever they want for a $10 part, just as hospitals can charge whatever they want for two aspirins that cost $3 a bottle at the drug store. With the price of gasoline, companies running service trucks are going to look for new ways to get customers to pay for a fill-up.
These capacitors have a range of value of approximately plus or minus 5 percent (this range may vary by capacitor). The microFarad (MFD) value range is on the label on the capacitor itself. So if the value the service man shows you is about 5 or 6 MFD for a 7.5 MFD capacitor, it is fine and doesn't need replacing. The sure way you know the capacitor is bad is when your blower motor does not operate.
At the least, tell the service person you know that the capacitor only costs $10 and you don't want to pay the inflated price they are asking. They will reduce the price. Gene Love originally wanted to charge $160. Boy, was I smart to get them down to $136!
Another caution: put a pencil mark on your capacitor (you'll find the capacitor mounted on the blower motor housing easily accessible by opening the blower door). Caution: turn the power off to your unit before opening the the door. That way, if a service person is showing you an old unit he or she brought with them, pocketing yours, you'll know it is not your capacitor. That's an old scam.
Both of my heating and air conditioning units, in Dallas and Columbia are less than 5 years old.