I think the financial side of it is a major reason for it today, and I think that explains it way more than a "Gnostic-like disdain for the body." I seriously doubt anyone chooses cremation with that in mind.
I think you are correct with regard to the financial side being a major reason. There are other factors as well. Many think that being cremated (possibly with ashes being spread about) is somehow a noble way to die. One would search in vain, I think, to find Scriptural support for such a thing.
In the early years of this country, there were exactly two (that's right, two!) cremations performed. One was done in 1792, when a former member of the Continental Congress requested cremation in his will out of fear of being buried alive. The second took place in 1876, and was overtly non-Christian, complete with readings from Hindu texts and Charles Darwin!
Do not discount subtle Gnostic influences either, my friend. Too many folks in our churches have the view that all that remains ahead is for the soul to shuck off the body, as if that is the final state. Very little (if any) thought is given to the resurrection.
I suspect, though, that if pressed, most would espouse a greatly affection for the body. Another minister communicated to me that once when a Christian was singing all the praises of cremation, he asked why the family couldn't just chop up grandma into little pieces with an axe. After all, that would be far cheaper than cremation and the remains could probably be stuffed in an even smaller box. Most folks are, of course, horrified (as they should be). It seems that the body has more value than first thought.
Here's a link to an exegetical study on this topic:
http://faculty.bbc.edu/rdecker/documents/Cremation.pdf
Also, I wrote an exegesis paper on Amos 2:1-3 a few months ago for a class, commenting on the subject of cremation within the context of the passage. I have posted it here:
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