I spend more time trying to unload all my loot (aka, jumping from city to city) then I do collecting it.
If you're in this situation and not willing to invest more perks in Speech to sufficiently buff the vendors, then you're best off changing your loot-or-leave threshhold[*] until the balance between time spent adventuring and time spent selling stuff is more to your liking.
[*] ie "it has to be worth 20 septims per unit of weight for me to bring it out for vendoring". If you're spending too much time running around for vendors, up that to 30, or 50. You'll carry out less money value per dungeon, but concentrated in the best-quality items so it's the least hassle to unload them.
If you take this approach after getting a high Speech skill, what it essentially means is that Speech is allowing you to get the same amount of gold for less player-effort. If you don't mind that that has contributed to your leveling up without contributing to killing power, that's a win.