Buy vs build in today's market

As the willingness to pay for decent quality businesses continues to rise, the argument for building seems to be more attractive each year. Take residential services for example, one could acquire a 4M revenue roofer doing 600k EBITDA for 4-5x and introduce a fairly cash sensitive situation into a seasonal business. Alternatively, you could stand one up from scratch, invest heavily into performance marketing and be generating a run rate revenue similar to that of the above company in about###-###-#### months (assuming you have the skills needed to hire, train and keep sales people and subs). Limited downside here, just some time to revenue ramp but no SBA, investors or PG hanging over your head. Of course, building something to a true $1M in EBITDA would take a lot more time and professionalization, but for those who are looking more on the mainstreet side.. have you thought about just building it yourself and then selling to a searcher? Seems to me like there's a gap here that people are willing to pay a premium for today.