>When the verb cost means to be priced at or to cause loss or expenditure, it is uninflected in the past tense and as a past participle. For example, we might say that the low-cost milk cost less yesterday than it costs today. But when cost means determine the cost of or set the cost of, it is inflected costed. For example, we might say that the store manager costed the milk at a cheaper price yesterday.
To people in the U.S., costed might sound funny because this sense of the word is not commonly used in American English. Americans don’t have an exact equivalent of costed, but valued, budgeted, priced, paid for, accounted for, and estimated the cost for come close in different uses. This sense of cost is much more common in varieties of English from outside North America, and it is not unheard of in Canadian English
tl;dr: it's Canada's fault
