I might pay $1.25 each for pick and choose, but not commit to an entire lot. I agree with Finn235 that you should instead pick a handful and start with those. I doubt your dealer has anyone else lining up to buy an entire lot of 100+ coins for that price, so they'll probably still be there if you want more.
If you are interested in these types of coins, buy the book also.
I agree there's almost no way you'd make your money back. Yes, you might enjoy spending a lot of time attributing the coins (or you might not) but there's not enough demand for attributed Ming coins for you to make your money back.
I would also ask do you have any other cast Chinese coins? I wouldn't start with 150 Ming coins when Qing and Song coins are so plentiful. Another fun area is the dragon coins from the early 1900s.
You could spend the same amount of money in multiple smaller lots over time and obtain a more diverse, fulfilling collection.
I wouldn't clean any of these coins. Even with ancients, one rule is to clean only enough to be able to attribute, which usually isn't a problem for this type of coin.