“I casted my net of submissions to the editors on my list. It costed me a ton in postage.”

Makes me think of the preschoolers I teach and not educated writers.

I would take issue, however, with your calling these uninflected verbs ’strong’ . Linguistic scholars call ’strong’ those verbs in the Germanic languages that undergo ‘ablaut’ in the past tense; that is, the stem vowel is changed; ’sing/sang/sung’, for example. ‘Have/had/had’,and the group with a final -t, such as ’sit/sit/sit’, and our present examples like ”cost/cost/cost’ are a different case. Here the expected -ed would, because the preceding consonant is voiceless, also be voiceless. In other words, it would be heard as a -t. The result is that it is not heard at all and is not written. This means they are slightly irregular ‘weak’ verbs, not ’strong ones.

It is, nonetheless, interesting to note the trend towards regularizing these verbs, as you show. This is part of a wider regularizing trend in English, no doubt driven by the large number of speakers who acquire it as a second language and do not therefore have a native speaker’s ‘ear’.