That sounds really expensive ... hard to imagine how much he charges an hour for his dozer ... my guy charged $85/hr ... larger dozer may be $110. My 28,000 sq ft (about 2/3 acre) pond cost me about $4500. Rural "downstate" Illinois is cheaper than many places, but certainly not THAT much cheaper.
I had a few trees along the "ditch" to remove, and moved quite a bit of dirt. I had one side with nice clay for the core, so that helped. I said what trees I wanted to keep, he knew stuff I didn't of course, so we figured it out ... it all went well.
I'm considering a ten acre pond (lake?) next, so may look into buying a scraper and dozer and doing it myself, though I'm not really a big equipment guy. But maybe for 1/8 acre you could oversee and talk, and just get a guy to work by the hour.
Not sure if you are wanting it eight feet deep in part, and you have to pay extra to load and unload the dozer, but it sounds like a one day job, maybe 12 hours? Hope you find the right guy.
I had another little ditch I had to dam up for access, and behind it is a one tenth acre "pond", but only four feet deep. It took about 2.5 hours to build that, with a wider than needed levee (the top right of the below pic ... dark green shows new grass on the levee.
The second pic shows the guy pushing clay into the core. It was 2012, really dry, but there was a little moisture. It was just tracked in, but seems fine. Pretty wide on that pond too I think.
