I'm sure creating the first spreadsheet application was more expensive than hiring an accountant. But not doing it 1 million times. Someone will make "contracts as a service" and competition will drive down the cost, until it's nearly free (as spreadsheets are today).
I think there may be a difference. Accountants are humans that are trying to be computers.
Smart-contracts are computers trying to be human. Most contracts are flawed and only really matter when things go wrong. I'd rather that a human be there when things go wrong to understand the human intent behind the contract than have a computer which does not know the human intent, but is able to enforce the (likely flawed) computational representation of that intent.
That's a tradeoff left to the contractual parties. The same human process that infers ill-specified intent can be corrupted to not execute that intent. If you want a human bootstrap, you hire a lawyer as an oracle which decides whether to process the contract specified in the blockchain.
I would guess that hiring a contract developer to create a water-tight contract the computer is capable of understanding would be much more expensive than a lawyer.
This is in a similar vein to the fact that it's more expensive to have programmers create a perfect NLP app to translate something than it is to just hire a translator. Translating english into other languages is not a solved problem. Whether that other language is french or a smart contract does'nt seem that material.
It does seem like it will be much cheaper to make contracts in bitcoin that don't require translating thousand-line-english-documents into a smart contract.
However, you can already do that without a lawyer. If me and you sign a paper saying it's a contract that "I will pay you $200 for an item delivered on date X/Y, and if you're late I pay $20 less per day it's late", that's already legal and enforceable without a lawyer.
Coding that same thing in bitcoin would be harder than writing it on a paper still I think.