cost well you shouldn't need to apply for FLR if your on a spouse visa (unless you entered the uk more than 28 days after your spouse visa was issued, you need to apply for FLR if your on a fiancee visa within 6 months of being in uk and being wed.

so i don't see how spouse is more expensive , becuase the next stage for both visa's you need to pay and apply for ILR. so a spouse visa is cheaper, unless i've missed something