My current small block cost me around $3500-4000 to build in the mid 90s. It runs 12.2s in Denver, which would be mid 11s to you sea level guys, and would be around 125 mph in a car that weighs 2950#. I've had this combo for about 15 years and have only needed to adjust valves and change oil and plugs. Last time I checked bearing clearences, they were still spot on. It is easily capable of 8000 rpm and I've had it there before, but I granny shift it at 6500 and it has lived a sweet and happy life without a lot of fuss for me.
If it lets go, I may consider going big block, but for now it fills the bill quite nicely. Sometimes you just need to run with whatcha got.
By comparsion, my bro has a Charger with a 440 six pak set up in it. Basic stock rebuild,not sure what it cost since it was done before he got it. His runs low 14s at 110. So they are actually close in power, I'd imagine close in cost, the small block may have been a bit cheaper since I did a lot of the work myself. If I applied the same approoch to a big block that I used in the small block, would it outpower the small block? I'd have to think so. But for now, my 360 runs comparable to and better than any number of big blocks I know. But, with that said, my small block is certainly not as street friendly as most of those same big blocks.