First you ignore anything that paid into escrow. That's your money, just held in a different place. Some part of it might become a tax deductible property tax payment whenever the tax bill is paid, other parts of it are non-deductible hazard insurance payments.
Assume the selling price as listed with the county clerk's office (on which transfer tax was paid) was $535K. Your parents essentially gifted you the amount of the down payment, in the amount of $150K. That means that what you paid was $385K. That's your starting cost basis.
Then, you can include the following closing costs.
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Abstract fees (abstract of title fees),
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Charges for installing utility services,
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Legal fees (including fees for the title search and preparing the sales contract and deed),
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Recording fees,
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Survey fees,
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Transfer or stamp taxes, and
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Owner's title insurance.
Other closing costs are not adjustments to basis. See here for more
https://www.irs.gov/publications/p523#en_US_2021_publink100010751
Those closing cost adjustments might add up to the full amount of the loan, or they might not, because I don't know what else was included in the loan. The loan might have included unallowable costs, such as an application fee, bank attorney fee, cost of obtaining a credit report, and other items also listed at the link above.
Since your cost was more than your parent's cost basis, and they (presumably) didn't pay gift tax, that's as far as you need to go.
If you bought the home from strangers for $175K cash to the owners plus $207K in lien payoffs, your cost basis would be the same or close (I get $382K, maybe the numbers are not precise) plus the same adjustments above. You have to get into the "gift of equity" situation because the home was worth more than you were providing in funds and your parents are related to you. But if you were buying the home from strangers, they have no legal requirement to maximize their profit and they could sell to you for less than market rate and I don't even think you would have to call the difference a gift, because they aren't related. (But I could be wrong about that.)
In any case, your basis really is the same as it would have been if you had bought the home from strangers for the same loan payoffs plus cash, plus adjustments for those closing costs which are allowed in publication 523.
