Yep, and there are plenty of small shops (far more than those that work on Porsche) who will work on the Corvette for far less than a GM dealership as well.
No matter how you slice it, long term costs of ownership for a Porsche will be higher than a Corvette.
It does not make either marque better than the other.  It is just simple economics.  Parts costs more for a Porsche.  Labor costs more.  It is the cost doing things with finesse versus a sledge hammer.
2009 porsche 911
                 YEAR 1 YEAR 2 YEAR 3 YEAR 4 YEAR 5       5 YR TOTAL 
Depreciation  $7,853 $7,041 $6,545 $6,351 $5,982       $33,772 
Financing       $4,160 $3,360 $2,480 $1,558 $556         $12,114 
Insurance       $1,938 $1,938 $1,938 $1,938 $1,938      $9,689 
State Fees     N/A N/A N/A N/A N/A N/A 
Fuel             $2,135 $2,364 $2,618 $2,898 $3,209         $13,225 
Maintenance   N/A $304 $1,728 $31 $1,476 $3,539 
Repairs           N/A N/A N/A $734 $1,622 $2,356 
Cost Per Year $16,086 $15,008 $15,309 $13,511 $14,782 $74,695 
2009 corvette
Depreciation    $18,607 $8,547 $7,323 $8,586 $8,396 $51,459 
Financing          $5,548 $4,482 $3,307 $2,078 $741 $16,156 
Insurance         $2,437 $2,437 $2,437 $2,437 $2,437 $12,183 
State Fees        $198 $155 $148 $134 $129 $764 
Fuel                 $2,706 $2,996 $3,317 $3,673 $4,067 $16,759 
Maintenance     $179 $219 $2,412 $650 $2,632 $6,093 
Repairs N/A N/A $107 $231 $254 $592 
Cost Per Year $29,674 $18,836 $19,051 $17,789 $18,655 $104,006 
There is almost a $30,000 difference that proves my point. I would imagine that the amount increases  the older the car gets.