1- My lawn has a lot of dead bare places, which I de-thatched with a rake. It hasn't been fertilized or watered.  Should I overseed the entire yard with pure Centipede grass, a combination of Centipede and Carpetgrass, plant sprigs, or just keep it watered and let the yard "heal" it self now that the thatch has been removed? 

2- Are your prices for Centipede seed competitive?

1- My advice would be to try and let improved maintenance do most of the work for you.  You should first obtain a soil test through your local county extension agent.  That way you can check for the soil pH and also for the iron content of the soil.   Sometimes spots such as you indicated are part of a problem classified as "centipede decline".  This is caused by a variety of factors including over fertilization and improper mowing (usually not mowing low enough).  Also... nematodes can cause similar problems.  Your extension agent can also test for nematodes. 

You will want to fertilize using a good quality fertilizer such as a 16-4-8... Try to get one that includes 1-2% iron as a minor element.  Centipede is usually iron deficient and must have it supplied to grow properly.  Do not overfertilize centipede or you will end up with the problems you have again. 

As to seeding the bare spots.  I would only re-seed the spots that are thin or bare.  And on those I would simply use pure centipede seed at a rate of 1/4 to 1 lb per 1000 sq ft.  you can base the actual rate on how bare the area is.  If it is completely bare use 1 lb, if half, use 1/2 lb etc....  You will need to re-rake these areas that you seed, so as to cause some of the seed to get covered by your raking action.  You will need to keep the planted areas watered daily for at least 45 days for best results. Limit the heavy watering rate to only the areas you re-seed.  Too much water is not good for grasses.    If you do not water those areas, expect slower or less re-establishment rates from what you seed.  Centipede is slow to establish anyway... but I would think you should be able to get your lawn back in shape by late summer.

2- I believe you will find Seedland price competitive on Centipede seed.