Oh, I see. I thought that you meant "rate" as in 'price', but you meant rate as in 'speed'.
Again, I know of nothing official, but ...
Employee salaries are about 25% of the cost of 'manufacturing'. If we apply that to repair and use the Gunner's salary of 1000 credits per month as the wages of a typical worker, then 'the Maytag Repairman' (our generic fixer) can repair 4 x salary = 4000 credits per month = 25 credits per hour.
Dividing the cost of the repair by 25 credits per hour will tell you how long it will take one man to complete the repair. Obviously, two repairmen could do it in half the time; 10 repair men could complete the work in 1/10 the time.
How many men are available and convincing the shop owner to put all of his people on one repair is a matter for the GM and roleplaying.
I hope that this helps.
It is just my opinion based on a little 'real-world' statistics.