GoDaddy's $7.19 price ($6.99 + $0.20 surcharge) is hard to beat. GoDaddy has good customer support; one can actually call them.
Not sure if there are any GoDaddy transfer-in discount coupon codes, but if there are, you could potentially transfer-in .com domains for under $7 or perhaps even below registry cost.
Note that for some other extensions, such as .info, and even .net sometimes, the registry cost may much lower, so be sure to shop around. But for .coms, there are never registry discounts, so anything below $7 is rock bottom pricing.
Ron