I've no idea if your local rates will be similar to ours, but we have just had a 4.4 acre field mowed, turned, baled and wrapped for small bale haylage by a local farmer.
We got 230 bales and his bill was £720+VAT.
The sward was reasonably thick, but the grass was not overlong, so that's not a huge number of bales for that size of field.
Our guy is very local to us, and didn't charge us for travel time.
There was a price per bale for baling and for wrapping, plus an hourly rate for mowing, turning and rowing up.
I imagine large bales will be cheaper for the same amount of grass.
Oh, and despite the username, I'm in North Cornwall