How much does limited basic cost?
Varies by the market, so you'll need to go to comcast.com and type in your zipcode, then look up pricing on their packages. I'd also google or bing comcast tv packages to see what unadvertized stuff they offer, as the salesperson is trained to sell you their most expensive package in each category and won't mention other stuff unless you ask about it first.
And expect them to pitch you on their "triple play" Xfinity stuff as well. I'd inquire as to what the normal prices are after the initial discount rate expires, as for example Comcast offers their triple play to new customers in my area for 6 months at $100 a month, afterwards the normal price is something like $145 a month...