Slates don’t cost that much on a per unit basis, like $4.00 each. Slates are still quarried from family quarries in New England, Pennsylvania and Virginia. If you need alot and special shapes, the quarry will cut them for you.
The “roofer” you talked to is probably part of an affinity rewards program with a roofing materials corporation. He gets points for every roof he sells. If he gets enough points he takes his family to Hawaii. The roofer you talked to does not get points for a couple slates. Slate doesn’t get him to Hawaii.
Find a roofer who knows slate and has the equipment to get up your roof. It’s the equipment and getting up there that is expensive, not the slate, so once he’s staged up there have him replace all that make sense. A bit of preventative replacements. Replace slates once in a while, as needed, and a slate roof can last forever.
Get slates at Roofing Center’s Slate Hill in Bethesda. They can recommend guys who do slate.
Watch this guy replace a slate in one minute: https://www.youtube.com/watch?v=Pf8xdbtiCM0&list=PLCAFA8B61D36361D8#t=469