I only use standard promotion, so can not say if one performs better than others, most of my promotion rates are at or lower than ebay recommendations, which also allows me to reduce prices on unpromoted items.

If you are promoting the glasses at 25% then approx  38% of your sale is consumed in ebay fees, add to that the cost of providing free postage is consuming approximately another 12% of the sale price, so you are clearing approx 50% of your sale price.  Not sure what makes your glasses higher value than many others on ebay, but you might like to try significantly reducing you buy now price and deleting or heavily reducing promotion rate, you may even have room to then add a postage charge to the listing, to recover some of the savings actually passed on to the buyer.