Morale and Competence bonuses can also provide bonuses to saves, though we already have a source of Competence bonus for Will (Channel Vigor: Spirit).
25 (bonus of 5 squared) x 2000 (base cost) x 3 (insight, sacred, morale) x 1.5 (to add to an existing item, assuming the item has a more expensive effect) x .2 (gold to IM conversion) x .5 (item creation cost) = 22,500IM
I'm unable to find any rules on minimum caster level for Saves Bonuses, but assuming the standard of 3 CL per 1 bonus, +5 is definitely within our reach.
A continuous item of Ruin Delver's Fortune provides a +11 Luck Bonus to Will (and might be able to be changed as an immediate action to one of the other effects?) and runs at
4 (SL) x 7 (CL) x 2000 (continuous item) x 4 (spell measured in rounds) x 1.5 (adding it to another item) x .2 (gold to IM conversion) x .5 (item creation cost) = 33,600IM
Dany's Persistomancy provides a +4 Morale Bonus to saves and a +6 Resistance Bonus to saves, but is not listed as a default bonus to our saves so it may or may not have been included in the rolling.
If that's the case, adding a Resistance Bonus of +5 to all saves will cost 3,750IM to make.
(25 (size of bonus (5) squared) x 1000 (price of Resistance bonus item) x 1.5 (adding it to another item) x .2 (gold to IM) x .5 (item creation cost))
We could also slap +5 Luck bonuses to Reflex and Fort saves for an additional 5,000IM assuming that the 3.X formula for "When targeting specific saves for created magic item bonuses, just reduce the price by 1/3 if targeting two saves or by 2/3 if only targeting one" applies.
(25 x 2000 x 1.5 x .2 x .5 x 2/3)
To summarise, for 56,100IM we would get +15 to Reflex and Fortitude saves and +26 to Will saves. Assuming 3.X rules apply for creating items that buff less than all three saves, for an additional 5,000IM our save bonuses would receive +20 to Reflex and Fort and +26 to Will. If Dany's DMM Persistomancy is not accounted for by DP, then for an additional 3,750IM that would bump up to +25 to Reflex and Fortitude saves and +31 to Will saves.
Tldr; The power of money can basically more than double our saves, and assuming all of the above applies it would cost us 64,850 IM to do so.
Also I want to slap this all onto our Crown so it's really swanky, but then we wouldn't be wearing our Mind Blank item.