Legal really will depend on the firm. For my exit, I used a boutique firm that ended up costing around $75k, but when I spoke to even my friends at the larger tech legal firms like Orrick, they wouldn't even consider it for under $250-300k.
We also just went through an acquisition and had legal costs in the same range. One thing that really helped us on that front was that both our attorneys and the acquiring company's attorneys were really forthright about not just the negotiations and modifications to the agreements, but with our motivations and reasoning for such changes, so that each side was actually able to help the other side figure out what changes should be made. This also helped us identify very early which changes were immaterial which allowed us to move along quickly without getting bogged down in semantics.
It can be pricey.