Pretty simple really....it makes sense because the Avs need offence and have plenty of cap space.
Please do list your multiple reasons on why this would be so bizarre.
Okay, since you asked:
(1) Eberle is slightly older than Barrie, although perhaps not enough to be significant. Sakic has repeatedly stressed that the Avs need to get younger in the offseason.
(2) Eberle plays a less valuable position than Barrie. This is compounded by the fact that the Avs have been desperately searching for D-men for several years and they have no one within the organization to replace Barrie's skill set.
(3) Eberle makes slightly more money than Barrie and has one less contract year remaining.
(4) Eberle is represented by Newport Sports. You know, Newport, the agency that Pierre Lacroix refused to deal with for years and had a public spat with Don Meehan. The same Newport that represented ROR during his tenure with the Avs and the same agency that represented Barrie last year when the Avs went through an arbitration hearing with him. The Avs have a long history of not being able to negotiate with Newport. The end result, Eberle is unlikely to be re-sign IMO after two years.
Taking all of the above into consideration, why would the Avs make this trade? Oilers fans may respond with "well we will throw in a later round draft pick or prospect." If the Avs keep Barrie for two and a half seasons and trade him as a pending UFA at the TDL in 2020, they very well could net a late first round draft pick and a B level prospect based on history.
You add it all up and, like I stated previously, it would be a bizarre move by the Avs. It has no significant positive impact for the Avs in the short term and no foreseeable impact in the long term, at least on the surface.