You will 100% get more money if you sell them seperatly. As to pricing, we can't see your playfield but my recommendation is to always look at completed listings. Here is Pinbots https://pinside.com/pinball/market/classifieds/archive?s=1&radius_latitude=39.00178&radius_longitude=-76.68747&keywords=&ad_machine_key=923&ad_condition=0&machine_type=&ad_machine_manuf=&year_from=&year_to=&radius_distancekm=0&sort_by=ad_end_date&sort_order=DESC#results and you can change the machine to bride of pinbot to get similar answers to it. Look at the most recent completed sales that look to be in similar condition to yours, and set that as your floor maybe adding 10% to it.

I'd guess $3000 on pinbot as the starting point. Now, you also have a relatively cheap excellent "starter pin" there and this would be one of the few pins I'd recommend cross advertising in other places (after giving Pinside folks a shot at first). First time pin buyers don't always grab their pins from pinside.

You can always reference pinbot in the bride of pinbot for sale add and offer to sell them as a package for $300-$500 cheaper total if they buy both. Most people want a discount if they are getting a package deal.