there are many ways to cast a powerfull spell without a *very* high spellcraft BASE modifier.
First of all: add mitigating factors to the spells (seems obvious I know

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Maximize your primary stat to obtain the maximum bonus possible (if your score hit 40, via buffs, increase, items etc... you gain a +15 bonus to the spellcraft check).
Don't forget sinergy bonus (knowledge: arcana grant a sinergy bonus to spellcraft checks if I remember correctly)
Take skill focus (spellcraft) and Epic skill focus (spellcraft)
Buy an item that helps. By the RAW, an item that grant a flat +30 to an ability check, ISN'T EPIC. So, you can have a +30 spellcraft ring (for example) at non epic cost.
If you have an artifact (in some epic campaigns is possibile to have one all the time), use it as a focus for you epic spells. This grant you a -20 to the DC of the spell (this particular mitigating factor appear in the "channel greater celestial" spell in the Book of Exalthed Deeds, thus we can assume is OFFICIAL). Of course, this mitigating factor is not valid for every campaign, because you NEED to have an artifact (and many DM don't use them).
Other than this...you can go with the rituals. If you have a spellcaster cohort, you can ask him to spend a spell slot to help you cast the epic spell (a 9th level slot is worth a -17 on the final DC of the spell. You can obviosly do that even with your friends PC.
Well... that's all. I agree with you, the epic damage-dealing spells are not powerfull compared to the non-epic ones, but you can indeed make wondrous things impossibles with the normal spell sistems, and combine effects to obtain the spell you have always dreamed.

But it's even true epic save or die are nasty, because you can up the DC a lot, and in 3.5 with the horrendous nerfing of every feats for raise up the spells DC, this alone worth the epic spell you can research. (my opinion, of course).
Take a look on the epic monster saves...brr...it's hard to survive for spellcasters in 3.5
To get rid of the XP points needed, the only "official" way is a rod of excellent magic (I hope the english name is that). If you break it during the spell research, you don't pay the XP needed.
(BTW, I think the XP needed to research an epic spell are simply ridiculous...the spellcaster, without burning the rod, need always to burn up a level or maybe the XP equivalent of 2-3 levels....bleah)
A good note, btw, is that epic slots are in addition to normal spell slots, so you can rely on these even when you run out of normal spell slot. A normal wizard hasn't the epic slots if don't pick up the epic spellcasting feat.
Hope this help

to me epic spellcasting is very funny, because the player can create what he want, not only what the book say.
Of course, the only way to make the epic spellcasting sistem work, is a GOOD DM, who can help you and prevent the obvious loopholes the system have.
have a good game!
Shariell