Although I can see the logic in "upselling" gutter cleaning & keeping it a seperate sales item, we include them in our bids for siding cleaning. There's a couple schools of thought here. Yes, the value of cleaning the gutters should be represented in your proposal. However, in my experience, the more options you allow the customer, the more conviluted your proposal gets.
Why not just include the gutters in the overall proposal, add in for the cost, and use it as a "differentiation" point when you're selling your service? If you're a bit higher than the other guy, explain that because you want to do a better job than your competitor, you ALWAYS do the gutters, where the competition adds it on. You're representing yourself as doing a complete job right off the bat. If you have to, take away the gutter cleaning and reduce your price. This is a basic sales approach which allows you to remove a service from your original proposal to reduce pricing, allowing the client to make that decision. Now the "take away" sales tactic comes into play. People don't like to believe they'll "miss out" on something, so 9 out of 10 times they'll go for the whole thing. Segmenting your service offerings in a proposal can come off as "piling on" or "upselling", which may cause the client to hesitate or be confused by your pricing structure. I firmly believe that you'll get more contracts by adding in the entire job right away. Good Luck!