May I ask, who was the expert who examined this? From the scan, this looks to be the more common rose stamp of 1886, Scott #43, not the #38 that better fits the price given. Further, did that person note the quotation was "catalogue value", which is an idealized number for a mint high-grade stamp? In any case, the real value here would be much less vs. catalog value, since it is without gum and has corner creases. It also looks to be a used example with a very light or faded cancel on the right side.
In actuality, a straightedge margin copy like this would have a reduced value against catalog value. Stamps with perfs all around are very much preferred. Check out the "sold" listings on eBay
for a more accurate idea of what this stamp is worth and to see how relatively common straightedge examples are.