I would not put pillars beside the middle of the driveway. You already have many beds and single trees in the lawn. Adding pillars beside the driveway would just be two more items to make the yard "busy." The best choice I can see would be to build short pillars or short walls in the center of the beds you already have where the driveway joins the street. If you have enough stone, quarter circles which begin parallel with the street and end parallel with the driveway. Height would be in the neighborhood of 2-3', possibly higher on the driveway side. This feature would be an echo of the house, but without adding more "busyness" to the yard. Another possibility would be to build pillars the same width and height as the porch columns to support a birdbath saucer, gazing ball, or some small piece of garden art. But placing these would be difficult. They might do well in the beds to either side of the front porch -- but the photos don't show the size of those beds, and adding pillars might overwhelm the plantings. Another possibility might be to replace the light at the intersection of the driveway and walkway with a light which sits atop a column; again I'd make the stone no higher than 3' (not sure how it would look if it were higher than the porch columns). You could do something similar with the post which bears the house number and its light, though there the stone could be higher. Or rather than make pillars for both lights, only the one with the house number, and make it more substantial than the porch columns.

That's my gate. I looked for tickets on the columns materials but we were building fence at the time too - mortar was 130, couldn't find a ticket for the block but DH said the columns are about 4ft and 5ft tall (have to have the tops even on the slope). Poured footer with rebar, laid cinder block and poured concrete into the bottom two rows of block for extra stability. BIL is a brickmason, so DH poured footer and they laid the block. The stone was priced in with the stonemason and was 1800. I wanted the solid flagstone tops so it cost a tad more for those instead of using the other rock. imo, your 3K sounds a bit high for columns this size, since he's not providing the stone. fyi, when you start a thread, click "preview message" and under your preview there will be blanks where you can add a link: Here is a link that might be useful:

for my mailbox for my home in San Diego, after I redid the front yard (removed all the grass and walkways and put in pavers, a picket type fence and made it into an english garden) I used an old vintage bird house/nesting box, it was hand painted, square shaped with a roof that lifted up on hinges, I mounted it to the house just at the edge very close to the driveway. Never had any issues with the postmaster delivery guy and it was very cute (if I do say so myself). If I were you, I'd try to speak to whoever brings the mail and ask them what they think. If it's the same person every time, they would be the only one who would complain and report you (if there are regs in your area) so then at least you'll know what's ok and what's not. I wish I had pics of mine, but they are on the hard drive of my last computer.

When we lived in CA in the mountains we also had a PO box in the city and all the important stuff went there as we to lost too many boxes. Then all of us went together and demanded locked boxes. Our mail boxes were all in one area. Our delivery person fought this as he got paid per box and a locked group counted for one, not several. We then went to the main office and had a meeting and finally months later had our locked boxes, but we kept our PO box as this too was damaged occasionally but mainly when the carrier was putting mail into the boxes, some mysteriously either ended on the ground, or given to someone else. Not a good carrier. I do feel for those who are isolated and expect something, and find it on the ground (soaking wet and damaged or put by the wrong box--too lazy to take it to the right box etc) checks and letters scattered etc. It is sad that some rural carriers and others do not respect our mail and privacy. Our neighbors even had mail opened, and then put in the boxes. But we were 5 miles from the boxes. Here they do not seem to have a problem as our carrier is so very dedicated and really watches the boxes and roads.