Hi! I'm looking for the PRD link that discusses combining magical items of the same slot? Its a price of 150% more for the more expensive of the two magical items. Where is the PRD weblink stating this?
Here. Scroll down a bit, below the table, to the bit headed up in bold Multiple Different Abilities. And it's actually that each ability after the first costs 50% more than it otherwise would. All items that follow the pricing guidelines precisely make the first ability the most expensive one, and the cheaper ones (if any) cost 50% more.
Side note: if you're making an item from scratch, it is very easy to make the most expensive ability first and then add cheaper abilities (with the 50% price increase) afterward. But if you're adding an ability to an existing item, the 50% multiplier goes on each new power, regardless of the price. So adding Regeneration to a ring of Sustenance would cause the more expensive ability, Regeneration, to suffer the increased price.
So it's sometimes better to just make a new item from scratch than to add an expensive ability to a cheap item.