I have read over the insert on page 39 of the epic level handbook and am still confused by how it reads. The example shows a +50 sense motive modifier and the description says its a sense motive 25 to sense the suggestion. Is this saying it is an opposed check (which makes the most sense to me) with the sense motive getting a +50 based on the example suggestion. Or is it always only a DC 25 sense motive. Any thoughts or clarification on this would be most appreciated.
The Epic Level Handbook's table that's part of the epic Bluff skill description (39) continues the table presented in the Player's Handbook Bluff skill description (67-8). That is, the creature that's attempting to use the skill's suggestion-like effect on the target makes a Bluff skill check that's opposed by the target's Sense Motive skill check. The target gains a +50 bonus on this Sense Motive skill check because of the creature's attempt to instill the suggestion in addition to whatever other modifiers are already present. (Presumably, this is done as part of general interaction therefore taking at least 1 round but ask the DM if it's possible a creature can instill a suggestion in a target while creating a diversion to hide, delivering a secret message, or feinting in combat.)
Any creature can make a Sense Motive skill check to sense enchantment (DC 25), though many will fail. The text in the description of the epic Bluff skill simply points out that, while the effect of a Bluff check to instill a suggestion is nonmagical, the effect can nonetheless be sensed with a high enough Sense Motive result as if the effect were an enchantment effect.
I was confused by this at first as well, but it sounds like you about have it.
The Instill Suggestion use of Epic Bluff is an Opposed Check
with the target receiving a +50 on their Sense Motive to avoid being 'bluffed'; in this case the Bluff is actually the Suggestion status. (Sense Motive) The +50 is the 'equivalent' of a low range Epic Skill DC, but for an opposed check.
The DC 25 Sense Motive check would be for a separate person to recognize that the influenced character is not acting of their own volition. You'll notice that use's description is
This is identical to the effect of the suggestion spell, except that it is nonmagical and lasts for only 10 minutes. It can be sensed as if it were an enchantment effect (Sense Motive DC 25).
which is not 'Your Bluff can be sensed' or any similar verbiage.