The size of the calf isn't the main problem, it's that the heifer is likely to be tight as a drum. The hormones that allow the vagina and vulva to stretch are naturally produced in the last weeks of pregnancy. When you abort a heifer at 7 months, you're missing out on that. The calf is much smaller at that stage, but the heifer's ability to pass a calf is much smaller, too.Sure, as long as you're paying the minimum $500 to get a vet out here.. last time it was $1000... I don't know how it is for the OP though.
At 7 months I don't think the calf would be over 40-50 lbs which shouldn't be an issue
I assume you're talking Canadian dollars, so $400 US. That's not small change, but for a good heifer and a live calf that you wouldn't otherwise have, I wouldn't say it's outrageous.