This is makes it easy to answer the question: how much do resources cost. It turns out that all the resources in GTK+ currently weigh around 1MB.
ea9026e Inspector: Show directory sizes in the resource tab
gtk/inspector/resource-list.c | 62 +++++++++++++++++++++++++++++++++++++---
gtk/inspector/resource-list.ui | 31 ++++++++++++++++++--
2 files changed, 86 insertions(+), 7 deletions(-)
Upstream: git.gnome.org