I'd ask them what exactly is included in a 'map survey' and give you examples of when that would be useful.

For what it's worth: about five years ago we had our back yard fenced. Technically we were on two plots of 30' width for a total of 60' wide property. The surveyor set the property stakes for about $300 and for another $100 they worked with the city to officially "vacate" the middle plot line, so now we're technically on one 60' wide plot. The city has various rules & reg's about new construction crossing plot lines, so now if we ever expand the house or build a garage, we can use our full 60' width without more legal wrangling. A recently built in-fill house paid $300 for initial survey then found out about the rules about building across a plot line and had to pay another $300 for the surveyor to come back and officially 'vacate' their middle plot line.

There are different kinds of drawing deliverables, like boundary, Mortgage/MLS, location, topographic, ALTA, so ask them what the $800 provides. Better to ask to see an example as the terminology can vary a bit. That may help you decide if the extra money is worth it to you for posterity or for future sale or improvements.

It's 800 well spent if they are including property lines, topography, exisiting structures (house, etc) and trees above a certain caliper measurement. I can't get that service in either of our service areas for less than 3k!

Could you check with your city or county to see if they have your survey on file?