Spreads when executing savings plans

I think many people here invest through a monthly savings plan. In the last few days there have been one or two informative posts about when and on which stock exchange the various brokers carry out their savings plans. Is there an overview somewhere of the prices and spreads at which the brokers execute? If not, would you be interested in crowdsourcing something like this? We'll definitely come across a pretty nice number of ETFs and Br here at home