it really depends on your location. i pay equivalent of 40 USD [ 300 swedish kronor ] for 100Mbit/s down, 10Mbit/s up link. it's home-grade connection but works within europe as advertised. it's fiber-to-the-building.
there are problems with servers at your home:
- if you are serious about them you need ups'es at least and - if things become business-critical - redundant power lines or diesel power generator
- sooner or later you'll need redundant air conditioning
- it would be nice to get two independent internet connections - but for that you'll need BGP, your own AS number and PI address range - that's quite a lot of hassle, maybe not worth it at the end
- what about 2 weeks of holidays away from home - who will power-cycle hanged machine or switch? who will replace failed disk?
servers rented or collocated at some data-center will give you more peace of mind and at small scale i think will be cheaper. it's just economy of scale - it might be really more expensive to do it inhouse.
you can rent 1u rack server, quad core, 4GB ram, 500GB hdd, 5TB network traffic @ 100mbit interface starting ~150 USD/month. check http://www.serverbeach.com/ for instance.
edit: last mile connection you can get
if you're lucky and can get fiber to your place. price per Mbit/s will be ok, but if telecom needs to build infrastructure - startup cost will be prohibitive. sky and your wallet are the limits of bandwidth you can get.
adsl/vdsl connection over copper is most likely, but that's not suitable for anything except mail-server for couple dozens mailboxes or own webpage. depending on range you can get 1-2 Mbit/s up to 10-20 Mbit/s of upload [ if range is < 500m ].
third alternative is wimax or other wireless solution. this tends to work ok, startup cost is higher then for adsl but lower then fiberoptics. bandwidth - depends on price, can be 10-32-64 or even 600mbit/s [ last one is really expensive ].