The import repository I made should be around 50MB, yours is around 150MB. It looks like it still contains a lot of extra garbage.
The main reason is probably that it's a raw repository as generated by git-fast-import. The git-fast-import manual recommends running git-repack -f --window=50 on the repository afterwards.
I can't seem to get git-repack to do anything; it just says "Nothing new to pack.".
I usually use the following alias: [alias] packall = !rm -rf .git/ORIG_HEAD .git/FETCH_HEAD .git/index .git/logs .git/info/refs .git/objects/pack/pack-*.keep .git/refs/original .git/refs/patches .git/patches .git/gitk.cache && git prune --expire now && git repack -a -d --window=200 && git gc
But, in your repository, even that doesn't do much. So if I'd had to guess, there still is a lot of extra garbage in there; the question just is: Where?