Hello
I work at Xometry as a DFM engineer and production support. The topic of nested files is interesting but their management can vary between sheet part manufacturers, as some have the habit of creating the nesting themselves from the received DXF or 3D files.
Here's a complete article to explain the advantages of nesting, and shows a case where nested files are cheaper because the used space is reduced, compared to shapes placed next to each other without optimization:
https://xometry.pro/en/articles/sheet-metal-nested-files/

Unfortunately, I do not have the answer as to why the total price of separately encrypted files is almost the same as with a single nested file, but my hypothesis is that the total surface area of material required and edges to be cut are almost identical.
The nesting done by you can make the work easier for a sheet metal worker, especially if it is well done. Here is an excerpt from the article on margins and spacing:
"In the context of laser cutting, it will be necessary to maintain a margin of 6.5 mm, with a spacing of 0.8 mm between each piece"

In conclusion, I would also like to add that our algorithm is regularly updated and improved to provide an ever more accurate and personalized quote, and it's possible that the automatic quote already uses the nesting model to calculate the total material cost, which may explain why in your case, the prices are almost identical.