Basement crack repair estimates - who to trust?

[Gregory Banks]

Hi all, my LTR (Boston, built in the 1930's) has some cracks in the basement walls that I didn't think were too serious (owned for 10y, some water and flaking but mostly dry). A new owner in the condo building is worried about them and wants them repaired. Ok, fine. We got three estimates from masonry repair companies ranging from $7,500 (patch) to $35,000 ("do this repair now or you will need a major $80K repair"). They each have different stories about what is going on that are pretty different - how do I find out what is really going on in order to make this decision? Other BP threads seem to indicate a structural engineer could make the call, but that getting one is pricey. How would you approach this? Thanks for any advice you can offer...