Would Have Cost or Costed?

"Cost" can also mean to estimate or determine the cost of something. If you are using that meaning of the word "cost," then "costed" is the past tense and the past participle. So if some accountants wanted to total up a business's expenses, you could say they costed out the expenses.

Would have cost or would have costed?

Both cost and costed can be used; it depends on the sense in which you use them. if you use the verb cost as a linking verb to imply to have an amount of money as a price, then it doesn't change in all the tense forms i.e. the present, past, past participle. For example, it costs/cost/has cost me five dollars.

What is the difference between cost and costed?

"'Costed' is inflected for the dummy pronoun 'it' which is coreferential with the infinitive phrase 'to get all of that text painted on. ' 'To cost' is a transitive verb where the agent is the thing being purchased, which is 'it'.