Factors to consider :
- wrapping is fiendishly expensive, both the wrap and the additional processing (necessitating an additional visit with a different machine). In my experience, wrapping will more than double, maybe treble the cost of producing a bale.
- it's impossible to compare costs without knowing the distances involved, as diesel will be one of the biggest costs to the contractor, and unless you're practically next door, travel time will also cost them - one visit for mowing, almost certainly another (or several) for woofling, another for rowing up, another for baling and another for wrapping
- before you upset the contractor you've got, be very sure you can actually get an alternative in place when you need it. It's all too easy end up "in the right" but with your long grass still on the field as you go into winter...
If you switched to another contractor, would you end up having to sell your surplus? Can you in practise get surplus hay removed from the fields while it's still good? What about if it's a bad year and you had to wrap it all, could you then? (Can stay in the field longer but need squeezy arms to move it.)
Personally, I'd take the view that my 4 acres wrapped probably cost the same as 12 acres unwrapped, and the contractor is welcome to the remaining 3 acres unwrapped for the conveniences of :
- having a contractor who is reliable and will do what you need when you need it
- not having to have any money changing hands
- not having any worries about disposing of the surplus