Girls offering erotic massage services in Utrecht have almost entirely moved to online directories. There are some studios, here and there. There is for instance the renowned erotic establisment Salon 261 (https://www.salon261.nl/) at Eikenlaan 261 in Alphen aan den Rijn. It feels almost like a brothel but officially it’s a place where they rent rooms to independent sex workers and some of them offer also erotic massages. Alphen aan den Rijn is around 40 kilometres and a 30 minute drive from Utrecht but Salon 261 has some amazing ladies with great customer reviews and is worth the trip.
Studio Roses (http://www.bodymassage.nl/index2.html) at Gaanstraat 26/28 is also a long-standing venue for sensual massages. Prices for a sexy and relaxing massage in Utrecht will vary between €50 and €100 and do not include extra services, which you have to tip for.