I do agree higher consumer prices would be a likely outcome. But, personally, I don't think the porous borders are merely a breakdown of law & order, or even just evidence of unfairness (some immigrants jumping ahead of those following the legal process), or that their link to consumer prices should even be considered!
Porous borders, first and foremost, are a national security risk. If a border is porous enough that unaccompanied children and teens can cross it... don't you think those that wish to harm recognize that weak point in our defenses?... and will eventually exploit it? I'm concerned about the growing number of people from countries other than Mexico (or even from other than the South American countries) that have been caught crossing our southern border. They've picked up people from known middle eastern terrorist hotspots crossing the Mexican border. I mean... WTF? Sure, maybe they're just harmless migrants weaving their way across the globe... but maybe they're testing the border.
Would I personally pay more at the grocery store as a trade-off for having that known security gap corrected? Yes, I would.