Personally, I think you're being a little lenient with setting up sigil sequences. Those should require a time investment, if not the gold investment. A month of casting the spell seems more fair, in terms of setting up a sigil sequence. Or perhaps keep the year, but lose the gold investment for casting the spell when used in that way.

Alternatively, some means of using multiple casts of the spell to speed up the process. A 20th level spellcaster could cast Teleportation Circle 9 times per day, if they really put their mind to it. Even at a full year's worth of casts needed, that comes out to a little more than 40 days, which seems much more reasonable.