If you marketed it the right way i reckon you would get around that figure but it would be down to marketing and advertising,if you sell it as a specialised job and look the part you`ll get that price.If you do a good job and by that i mean get it looking like new people will see it as money well spent,how many home owners do you know that are prepared to clamber around on there conservatory roof with a brush,not many.It`s a joke some WC`s doing con roofs for £20-£30,for top money you need to sell it to the customer as a job in itself and not just an add on when your doing the window`s,i always say i`ll have to come back and do it another day,if they see you whipping your brush over it in 20 mins your never going to get top money for doing em.
