As I have found, the profiles are VERY cheap... the connectors are another story...
Take a look at what I 'made' to connect my profiles:
The little corners are available here for $1 for 4, the 8020 corners were 1 for $4... big difference!
Took me about a minute a piece with the Dremel (rotary tool) and some custom drilling, tapping, and I was in business quick!
Hope this helps;
DDL
I suffer from the Dunning–Kruger effect... daily.
get teh plastic connectors from thorlabs, 7$ or so or less.
Steve