The "always looking for the better deal" is really part of a larger scarcity mindset that's in our culture.
If you convince people that there isn't enough and that they better "get theirs" before it all runs out, then people will buy into all kinds of "upgrading." I've known married couples who would never make solid plans because they were always afraid they'd miss that last-minute opportunity of a lifetime. Or the people who have perfectly good phones who MUST upgrade every six months because they're told that the magical unicorn feature is on the newest version.
Another part of the problem with dating sites is that people are treated as product. There's not much difference between surfing Amazon for various books, movies, etc., and surfing a dating site. You get the little pictures. There's the clever sales pitch. You get the cost of the item (or the demands of the person). You read it all and decide if you want to buy...er...date.
Unfortunately, there are lots of Christiany ideas out there that feed the philosophies of scarcity and consumerism. Christian singles are told to look for their SOULMATE (not a biblical idea). They're told God has ONE PERSON planned for them (also not biblical). They're told to make lists of demands that SHOULD BE MET before they enter in to a relationship (again, not biblical). So we've got scarcity in the form of finding that ONE amongst BILLIONS on the planet. Seriously...ONE...What if the one is 12 and lives in China? What if your one is already married? What if your one is the NEXT profile you'd look at? And we've got consumerism in the form of "it's all about you" and "the customer is always right."
These kinds of mindsets exist outside of dating sites. They're just particularly honed at these locations. It takes a very strong and self-aware person to not dehumanize others AND to believe that what you have is enough.