Ares isn't wrong about the scaling of Reputation economy being a pain, but it has gone through some improvements -- when FC first came out, a level of renown cost a staggering 50 rep before the 2nd printing reduced that a somewhat more affordable 30.
Assuing you can get your GM to agree, my suggestion as to the simplest change would be to rescale the check result from TL+0/5/10/15/20 to something like TL+4/8/12/16/20.
And do bare in mind that what you're acquiring here isn't a check bonus
, it's a check result
. Which means that it has in effect already factored in all possible situational modifiers. So in situations where modifiers would work in your favour that probably gives you a crappy result, but OTOH pulling this out when all the negative modifers would inevitibly mean failure if your character attempted the roll, it suddenly looks a lot better.
The base state of the rules is that there is no magic, and that even if there is you cannot buy magic items.
Got a page reference for that no-buying rule, because it's not striking a bell? Unless you mean the mention that magic item purchase -- just like every other rule -- is ultimately GM fiat?