Yes, I need to run some tests to get the actual numbers to update the wiki page, but if a unit costs 100 m+c to repair, it will cost 100 m+c no matter what repairs it.
The repair rate is simply how fast the repair happens, so a unit with Repair Rate 2 will repair twice as fast as a unit with Repair Rate 1.
Reading the patch notes, I think repair costs are now 25% of the listed build cost but I am very uncertain about that at the moment, it might be 50% and it might be 12.5% depending on how you read them.
Will see if I can find time for those tests tonight.
D.