Tell him the price

It is not like you like being a prostitute was your dream but... By doing only two blowjobs you managed to equip yourself and there are many more adventures in the village with cash. One day of humiliation and you may allow yourself to buy expensive stuff from this or two other shops. "I only offer blowjobs. Quarter of a gold piece for a basic one" WHAT THE FUCK? You wanted to name your 'usual' price of 5 gold pieces but instead you say something very different. "I mean a quarter of a gold piece" Again you say not what you wanted to.

"Wow, It is really affordable. Will you... ehhhm... do it here or shall we go to the tavern?" Mage asks enthusiastically as you try to understand what happens. Luckily, quite conveniently, you get a text box with direct description of the problem. You are now not a usual NPC, but, essentially, a subtype of shopkeeper and they can only name price determined by the game economic system. It is like this game intentionally tries to ruin your plans.

With such payment rate you'll either need to do an awful lot of blowjobs or offer something more valuable to earn enough money for another shopping spree. In any case the mage waiting for your answer.

"So?" Mage asks impatiently