How much harder are the higher Sit N' Gos?

[Mother Mucker]

In my limited experience of playing sit n' gos (don't know how many games....played a few years mostly at Pokerroom), I noticed that the $5 tables used to be super soft but they have gotten just a little harder the past year or so (definitely not unbeatable though). I mostly play the $10 tables now and do decent at them but I recently jumped up and played a couplt $30 tables just for fun and they don't seem too different. They are a little tighter than the $10 tables, but not by much. Basically, what I'm asking is how different, in terms of "beatability", are the different levels of sit n' gos in your experience? I'm starting to think you can't compare the relationship between a ring 1/2 vs ring 3/6 and a SNG $10 vs SNG $30.

Thought?