Cheap paint not very long, it might start to fade and chalk at 2 years or less. Higher end paints last much longer.
Do not confuse brand names with products. Someone may tell you they are going to use brand x. You recognize the brand and think you’re getting quality. In reality they are going to use brand x’s lowest grade paint. The cost of paint can differ quite a bit and may explain differences in estimates.
Company A is going to power wash the house properly, remove window screens so they can mask more precisely, caulk gaps, fix open cracks, etc.... Then apply 2-coats of paint. Investing 40 hours of labor.
Company B is going to spray water at the house and call that power washing, attempt to mask around screens, which results in overspray on window frames. Leave gaps un-caulked and not repair cracks. Then apply a thin coat of paint. Investing 32 hours of labor.
Prep and repairs require time. It is easy to see how company B is cheaper especially if they use low quality paint.
Quality of paint as discussed above can be a factor. Paint cost aside consider this example: