The USPTO is proposing a 48% increase in government fees to obtain a design patent. The majority of this price increase is in the design patent issue fee, which is proposed to increase from $560 USD to $1,000 USD (large entity fees).
Filing fees are set to increase across the board, including fees for utility patents, but much more modestly. The full table of proposed price increases can be found here. As for an explanation as to why the fee increase for design patents is so disproportionate, the USPTO has only to say that it is because design patents are not subject to maintenance fees (see the PPAC Detailed Appendix, slide 72). This also explains the relatively substantial increase in plant issue fees from $760 USD to $1,000.
The fee increases put the large entity issuance fee for utility, reissue, plant, and design patents all at $1,000 USD.
Despite the stated justification for the design patent fee increase, it is worth noting that the USPTO might be expecting the number of design patent applications it receives to increase, having recently implemented the Hague Agreement for expedited design patent registration. The Hague Agreement reduces the filing cost of global design patent filings for U.S. entities, which could balance out the cost of global design patent protection overall.