I did an honors thesis and while it did suck (75 pgs), if you plan out your writing well and diligently work towards it each week (like 2 paragraphs per week, background done by month x, etc), it can be done. For the MD/PhD pathway it certainly help since you'll have to write a dissertation and articles - might as well get some practice lol.
Now the financial constraint is certainly a factor to consider - if the thesis route would be too burdensome, forgoing it won't prevent you from getting into med school as long as your other ducks are in line.